Eighth Death Blamed on Colorado Flooding

Sept. 16, 2013— -- An eighth person in Colorado has died and more than 600 people are unaccounted for in the ferocious flooding and relentless rain ravaging communities across the state, according to officials.

The body belonging to the eighth person confirmed dead was found in Clear Creek County, according to Micki Trost of the Colorado Division of Emergency Management. Few other details were immediately available.

Three prior victims were from Boulder County, and two each from El Paso and Larimer Counties, according to the Colorado Office of Emergency Management website.

While a total of 1,253 people had not been heard from as of Sunday evening, officials had cautioned that the number was subject to change as widespread flood recovery efforts continued.

The number had dropped by more than half as of this morning, with about 631 people unaccounted for statewide. The number stood at 648 this evening, according to Trost.

Among those missing earlier today, 398 were from Larimer County alone. But Nick Christensen of the Larimer County Sheriff's Office said officials "don't think the number will nearly be that high."

Those who evacuated or self-evacuated and have not registered with the Red Cross are also taken into account, he said.

Twenty-one military helicopters operated by the Colorado National Guard, the 4th Infantry Division and the Wyoming National Guard resumed the search this afternoon for residents cut off by the rising waters after being grounded Sunday, according to the Colorado National Guard's Twitter account.

With flash flood risks endangering at least 15 counties statewide, Colorado was "not out of the woods yet," the state's Flood Decision Support System tweeted.

More than 1,000 residents remained stranded in areas isolated by the rising floodwaters that have damaged or destroyed 19,000 homes, officials said.

Rescuers Seek Survivors and Signs of Hope

A National Guard helicopter carrying civilians out of Lyons, Colo., was grounded by heavy rains and floodwaters Sunday. The crew was forced to wait it out and spend the night on higher ground, according to a National Guard news release. It's just another problem in a continuous stream of misfortune for so many in the flood zone.

Colorado Floods Surge as Toll of Unaccounted Rises

The National Guard was working overtime and has conducted at least 400 helicopter rescues in what is now the largest aerial rescue operation since Hurricane Katrina in 2005.

Days of punishing rain and floods have transformed the mountain communities in Colorado's Rocky Mountain foothills from a paradise for backpackers and nature lovers into a disaster area with little in the way of supplies or services.

Roadways have crumbled and scenic bridges have been destroyed since the flooding began Wednesday.

The floodwaters are covering more than 2,000 square miles across 15 counties in Colorado, an area about twice the size of Rhode Island. More than 11,000 people have been evacuated, and there are still several evacuation orders still in effect.

The additional rain falling on ground that has been saturated by water since last week has left many people fearing that more flash flooding and mudslides could still happen.

PHOTOS: Dangerous Colorado Flood Waters Claims Lives

President Obama signed a major disaster declaration this weekend, ordering federal aid for the flood-ravaged state.

ABC News' Sam Champion, Clayton Sandell, Rachel Katz, Michael S. James, ABC News Radio and The Associated Press contributed to this report.