For On Going Live Coverage: Live Updates: Tornado Damage in Oklahoma Day 2

6:43 a.m.

President Obama will deliver a televised statement regarding the Oklahoma tornado at 10 a.m. ET.

6:28 a.m.

Pope Francis tweeted, "I am close to the families of all who died in the Oklahoma tornado, especially those who lost young children. Join me in praying for them."

5:33 a.m.

McClain County Animal Response Team spokesperson Dr. Patty Mannas told ABC News affiliate KOCO-TV that at least 50 pets have been pulled from the rubble in Moore, Okla.

"We've already reunited a few animals and animals with microchips have a very, very high percentage of being reunited with their families," she said.

4:20 a.m.

The death toll remains at 51 but the Oklahoma Chief Medical Examiner said they expect around 40 more bodies.

2:50 a.m.

Moore officials tell ABC News the search and rescue operation at Plaza Towers Elementary School is now a recovery effort.

12:50 a.m.

Texas Task Force 1, the state's elite search and rescue team, has been activated to assist local officials and first responders in Oklahoma. The team, which includes 84 total members, was deployed to New York City following 9/11 and to New Orleans in the aftermath of Hurricane Katrina. It was recently deployed to West, Texas, following the explosion of a fertilizer plant.

11:57 p.m.

President Obama signed a disaster declaration in Oklahoma and ordered federal aid to supplement state and local recovery efforts in the area affected by severe storms and tornadoes.

10:59 p.m.

Oklahoma Lieutenant Governor Todd Lamb confirmed to ABC News that at least 3 schools in the state were hit today. Lamb said that it may even be as many as 5 that were hit.

10:42 p.m.

Oklahoma's Office of the Chief Medical Examiner confirmed to ABC News that out of the 51 killed, at least 20 are children. The office said that it does not know how many of the children that were killed were at school at the time. The total number of people killed is expected to rise.

10:30 p.m.

VIDEO: Father Reunited With Son After Oklahoma Tornado

Moore Medical Center released a statement saying that it sustained significant damage during today's storm. At least 30 patients were there at the time were transported to hospitals in Norman, Okla.

"The Health System has been inundated with patients," the hospital said in the statement. "So far we have treated 25 patients at that facility, including a 9-year-old girl. Kaileigh Hawkins was at an elementary school that was damaged during the storm. She is doing ok, but her parents are not with her. We are asking for help contacting her parents. Anyone who may be able to contact them should call 405.307.2713."

Norman Regional Hospital is also treating as many as 35 "walking wounded." At this time staff and patients at Moore Medical Center have been accounted for.

Those looking for loved ones may call our patient care hotline at 405.307.1366. You will be instructed what to do if your loved one is being treated at any of our facilities.

10:15 p.m.

VIDEO: Surviving the Destructive Oklahoma Tornado

The American Red Cross released a statement that it has one shelter open in Moore, Okla., and is working on locating others. The organization said it will continue to operate three shelters that were opened Sunday in the Oklahoma City area following Sunday's storms.

The organization's volunteers are out tonight with food and supplies supporting first responders, it said. Over than 25 emergency response vehicles are positioned to move at first light Tuesday morning, and it is expected that the number will increase. The Red Cross is also sending in kitchen support trailers to support the upcoming operation to provide meals to those forced out of their homes.

10 p.m. ET

Statement by Secretary of Homeland Security Janet Napolitano: "Our thoughts and prayers go out to everyone impacted by the tornadoes and severe weather in Oklahoma, especially the families and loved ones of those killed, injured or missing. As search and rescue efforts continue, this administration - including the Department of Homeland Security and Federal Emergency Management Agency - will bring all available resources to bear to support state and local emergency management teams and first responders in the affected communities. We encourage the public to listen to direction from state and local officials."

UPDATED STORY: Children Among at Least 51 Dead in 'Horrific' Oklahoma Twister

PHOTOS: Tornados Slam Oklahoma

9:15 p.m. ET

The latest - at a glance:

• Fifty-one confirmed dead by Oklahoma Medical Examiner's Office.
• "Confirmed casualties" at Plaza Towers Elementary School, fire chief of Moore, Okla., tells reporters at news conference
• The Associated Press reports 120 injured in various area hospitals, 70 of whom are kids.
• EMS says around 100 patients transported by EMS to area hospitals.
• Moore police chief says search and rescue efforts will continue throughout the night.

9:10 p.m. ET

Officials at news conference confirm unspecified number of casualties at Plaza Towers Elementary School.

WATCH: Gov. Mary Fallin Discusses Tornado at News Conference

8:57 p.m. ET

At least 51 are dead, Oklahoma's Office of the Chief Medical Examiner tells ABC News. Children are among the dead but the medical examiner's office couldn't confirm a number.

8:40 p.m. ET

NEW VIDEO: Tornado Rips Through Moore, Okla.

8:20 p.m. ET

In addition to 37 confirmed dead (according to the Oklahoma Medical Examiner's Office - see 8:15 p.m. entry), 105 casualties were being treated at area hospitals - 85 at OU Medical Center, 65 of whom were children and 20 of whom were adults.

8:15 p.m. ET

Thirty-seven confirmed dead in Moore, Okla., Medical Examiner's Office in Oklahoma tells ABC News.

8:10 p.m. ET

New photos:

Rep. Jim Brindenstine, R-Okla., from the House floor in Washington: "At this time, we don't know the full extent of the damage and the potential human toll, but we are inspired. We are inspired by those who are sparing no effort to assist their neighbors and even many people that they don't know."

8 p.m. ET

The latest - at a glance:

• Oklahoma Chief Medical Examiner's Office tells ABC News at least 10 dead.
• Sixty patients admitted to area hospitals - 10 in a critical condition at Ingris Health Southwest.
• Two schools badly hit - Briarwood Elementary School and Plaza Towers Elementary School.
• Preliminary assessment by National Weather Service puts tornado at EF-4 with winds of up to 200 mph.
• Emergency Management Office says tornado cut a 12 mile swath through an area from Newcastle to Moore, Okla.

7:52 p.m. ET

Oklahoma Gov. Mary Fallin, according to ABC News Radio: "We want to do everything we can to search through these damaged areas, especially before it gets dark or before we have any more storms that might come through."

7:39 p.m. ET

President Obama has told Oklahoma Gov. Mary Fallin that FEMA stands ready to provide all available assistance as the governor's team responds to the storm and that he has directed his team to ensure that they are providing available resources as the response unfolds.

"The president has called me," Fallin confirmed. "He has offered to do anything he can to help with red tape to help with the federal entities. We actually had someone from FEMA that arrived yesterday."

7:34 p.m. ET

Oklahoma Gov. Mary Fallin, according to ABC News Radio: "Right now, we're in the search-and-rescue mode. We're desperately trying to look through the buildings, the homes, the community itself to make sure we can account for people."

7:32 p.m. ET

"We probably had five tornadoes (not sure about the number)," NOAA spokeswoman Keli Pirtle in Norman, Okla., emails to ABC News.

7:30 p.m. ET

Ten people confirmed dead in wake of tornado, Oklahoma Chief Medical Examiner's Office says.

7:24 p.m. ET

Red Cross Oklahoma tweets: Please RT: Shelter opening at: St. Andrews Church, SW 119 & S May. Location will also serve as reunification site.

7:23 p.m. ET

Emergency Management Office plans to hold news conference at 8.30 p.m. ET at City Hall in Moore, Okla., with several agencies to be represented.

7:20 p.m. ET

All children at Briarwood Elementary School have been accounted for, first responders on the scene tell ABC News.

7 p.m. ET

Oklahoma Lt. Gov Todd Lamb tells ABC Radio:

"It's devastating in Moore, Okla. It is absolutely devastating. This is horrific. The ferocity of the tornado. … We're going to have fatalities. … We're going to have significant injuries. … We just don't know what those numbers are. Schools have been hit, a hospital has been hit, businesses have been flattened, neighborhoods have been wiped away. We don't have the numbers in yet but it is going to be significant and it is going to be horrific."

6:59 p.m. ET

6:56 p.m. ET

6:45 p.m. ET

A sixth grade student at Briarwood Elementary School told ABC News affiliate KOCO in Oklahoma City that school officials told students to prepare for the tornado.

"I was in my classroom and we were told to get in our tornado precaution systems," the student, named Brady, told KOCO. "But when they moved us to the boys and girls bathroom, then some kids were not following directions, staying away from under the sinks and stuff, and they got under there and cinder blocks and everything collapsed on them. They were underneath, so that kind of saved them a little bit.

The student's mother, a teacher at the school, lay over her son during the tornado.

"She was on top of me," he said. "She was able to be with me."

The school was full of debris when he finally evacuated, he added.

"It was just debris," he said. "There was just cars beaten up. My mom was flipping out about her car."

6:40 p.m. ET

6:40 p.m. ET

6:35 p.m. ET

Students at Briarwood Elementary School hid in bathrooms as the tornado swept over Moore, Okla., students told ABC News affiliate KOCO.

They were then evacuated to a nearby neighborhood, where parents were being advised to pick up their children. No fatalities have been reported.

At Integris Southwest Medical Center in Oklahoma City, 19 patients came in with injuries from the tornado, including two 6-year-olds and one other child, as well as an 86-year-old and 91-year-old.

Seven patients were in critical condition, seven were in serious condition, and five were in fair or good condition, the hospital said.

Injuries at the hospital ranged from minor lacerations to severe head injuries and abdominal wounds.

6:20 p.m. ET

First responders are combing the homes and buildings of Moore, Okla., for survivors after a mile-wide tornado swept through the town near Oklahoma City this afternoon.

There are not yet reports of fatalities.

The National Weather service said that a preliminary rating of an "E-4? was given to the tornado, which ripped across Oklahoma today, destroying buildings and injuring dozens of individuals near Oklahoma City.

The National Guard has been activated in the state and was being sent to the Moore area to assist with disaster response.

Moore Medical Center, a 47-bed hospital in the town of Moore, Okla., was in the process of evacuating patients to two other hospitals in Norman, Okla., according to its spokesperson. The second floor of the hospital was ripped off as the tornado swept through Moore.

Schools in Moore did not release students at the end of school today in anticipation of the severe weather, the district said. One school, Briarwood Elementary School, was severely damaged, and the status of its students and faculty was not immediately known.

According to the Great Schools website, there were some 650 students in grades pre-K through 6 enrolled at the school. There are more than 22,000 students enrolled at 29 schools in the district, which has been highly-rated for excellence.

ABC News' Anthony Castellano, Kevin Dolak, Michael S. James, Colleen Curry, Lauren Effron, Jon Williams, Mary Bruce, Maria Nikias and others contributed to this report.