The desperate families of West Virginia miners still unaccounted for were told late today that holes drilled into the exploded mine shaft were beginning to help release the toxic gases that have kept rescue teams from going in to search for survivors.
A federal safety official said this evening that levels of carbon monoxide, hydrogen and methane were dropping at the top of the holes and levels at the bottom of the holes would be tested late this evening to determine whether it was safe for rescuers to go into the mine.
"The one thing that looks positive to us is we're seeing a downward trend and that's a positive thing," said Kevin Stricklin, an administrator from the federal Mine Safety and Health Administration. "We just want to make sure that downward trend isn't deluded."
He said rescuers could go into the mine overnight if it is determined that the air is safe.
"We've basically asked the rescue teams to come to the mine site and they're ready and prepared to go underground as needed," he said.
Gov. Joe Manchin said the families of the four miners still missing from Monday's blast "realistically understand the sliver of hope" that the men could have survived the explosion and poisonous air.
Nevertheless, they "understood and were very agreeable" to the idea that fresh rescue efforts would have to wait to be sure rescue crews are not put in danger, Manchin said.
The explosion in the Upper Big Branch mine killed 25 miners.
Immediately after the disaster, rescue crews rushed into the mine, but were quickly forced to retreat because of the toxic conditions.
Manchin said that the only hope the men were still alive "is they made it to a chamber," referring to a specially constructed shelter in the mine that would provide them with clean air.
A refuge chamber sits 300 feet to the right of the first hole emergency workers drilled. It is four feet high and 20 feet long, room enough for 15 miners. There is 96 hours of oxygen in the chamber, but the supply would last longer if there were fewer men in the chamber.
Efforts to contact any survivors earlier today by banging a pipes failed to get a response.
For the first time today, images from inside the gates of the mine were seen from a location where teams were drilling some 1,100 feet down.
At one point, when the rescuers broke through a wall of the mine, air began to rush in -- a vacuum effect the workers weren't expecting. They had to place a fan on top of the drill hole to suck air out. That's when their tests finally revealed it was toxic.
When crews get the all clear, rescuers will enter the mine and ride what is called a "mantrap" for 30 minutes. From there, they will walk the rest of the way to the refuge chamber in search of survivors.
While the families of the missing men wait in agony, clinging to any shred of hope they can muster, the community remains stunned and angry about the loss of the rest.
Timmy Davis Jr. lost his father and two cousins in the explosion.
"He would tell us sometimes about how dangerous it was, but it didn't bother him," Davis said of his father, Timmy "Big Tim" Davis Sr.
"He just loved his job," he told "Good Morning America" today. "That's where he liked being at. If he made it out, he'd go back tomorrow."
Davis said his cousins, Cory Davis and Josh Napper, were "just good kids, trying to make a living."
Davis had driven a coal truck at the mine. But he was laid off, he said, the day of the explosion. Now, he's considering leaving his home state and starting a new life away from the mines that have employed his family for generations.
Officials believe the blast was caused by a build up of methane gas, a constant threat deep in the mine.
Stanley Stewart, who was about 300 feet underground starting his shift when the explosion hit, described it as "hurricane-force winds." The blast could be felt for miles.
"I told my friends, 'Take your time, so you don't fall.' I was trying not to panic, panic was setting in," he said. "I knew it was bad."
Once out, Stewart said, he immediately volunteered to go back in to pull his friends out but was not allowed to make the rescue attempt.
"Some of the company personnel found some people that were killed," he said, crying. "Some of those were my buddies."
Gov. Manchin: 'I've Never Seen Anything Like It'
Rescue workers were chased out of the mangled mine by poisonous gases early Tuesday. Officials said no one would be allowed back in until the air could be tested to ensure the rescue workers' safety.
Nearly everyone in the community surrounding Massey Energy Co.'s Upper Big Branch mine near Whitesville, W.Va., has been affected by the worst mine disaster in more than 25 years.
"I've never seen anything like it," Manchin told "Good Morning America" Tuesday.
"I don't understand why it had to happen," Janice Florence told "World News With Diane Sawyer." "I thought they had things like alarm systems and things that would go off in the mines.
"They need to be safe," she said. "I just hope they get to the bottom of this."
President Obama Tuesday asked for prayers for the men killed, their families and the rescue workers trying to find the miners still missing.
"May they rest in peace and may their families find comfort in the hard days ahead," he said from the East Room of the White House before an Easter prayer breakfast.
Obama reiterated his offer to the West Virginia governor that "the federal government stands ready to offer any assistance that is needed."
With the vast improvements made in terms of mine safety, technology and education, an explosion of this proportion was likely the result of a perfect storm of events, according to Mike Rohaly, a retired mine engineer who spent about 15 years of his 35-year career underground.
"In this day and age this kind of mine disaster is unheard of," Rohaly said. "A lot of bad things have to happen at the same time, in my opinion."
While the tight-knit community is now bonded in shared anguish and grief, Rohaly said he'd expect a range of emotions as friends and family learn more about the accident.
"I'm sure the response will vary all over the board with the miners and their families," Rohaly said. "Some of them will go right back to work, some of them will not have anything to do with mining and move, do whatever they can to get away from it."
Mine Explosion: Distraught Families Wait in Anguish for News
Richard Scarbro, whose friend Deward Scott was killed in the blast as he was leaving the mine at the end of his shift, said "there's no answer."
"We got loved ones to take care of," he said. "Families without fathers, families without grandfathers ... some children not being took care of."
A Facebook page that sprung up shortly after the blast and quickly grew to tens of thousands of members listed condolences, prayers and outrage at mine safety.
"My father was a coal miner in WV in the 1930s," one poster wrote. "He told me of running out of a coal mine as fine, silty dust trailed behind him. It appears mining is NO safer now than it was then!"
Massey Energy is one of the nation's largest coal producers, but has had a spotty safety record. The company paid out millions of dollars in fines last year alone after admitting to repeated safety violations.
Manchin said an investigation would come later.
"I don't know what happened," Manchin said. "We're going to find out and do everything in our power to never let this happen again."
ABC News' David Muir, Cleopatra Andreadis, Desiree Adib, Lee Ferran, and The Associated Press contributed to this report.