• West Virginia State Police direct traffic at the entrance to Massey Energy's Upper Big Branch Coal Mine
At least four others were still missing more than 1,000ft underground early today after the blast in southern West Virginia, the worst US mine disaster since 1984.
Rescuers had been making their way to the area where the miners were believed to be trapped at Massey Energy's sprawling Upper Big Branch mine, where the explosion happened at around 3pm yesterday (1900 GMT).
However, safety officials said at a news conference that the search had been suspended because rising methane gas levels in the mine made it a high risk for another blast.
Earlier, Kevin Stricklin, an administrator for the federal Mine Safety and Health Administration, said officials hoped some of the missing had survived the initial blast and were able to reach airtight chambers stocked with food, water and enough oxygen for them to live for four days. However, rescue teams made it to one of two nearby shelters and it was empty. The gas levels prevented them from reaching the second.
Massey Energy and safety officials confirmed that 25 bodies had been found. The death toll had risen from seven earlier in the day to 12 at about midnight. A total of 29 miners were in the area when the blast happened, he said.
"It does not appear that any of the individuals made it to a rescue chamber," Mr Stricklin told the news conference. "The situation is dire."
State mining director Ron Wooten said that, although the chances of reaching the four still missing looked slim, rescuers would not give up.
"We haven't given up hope at all," he said.
It was the worst mine disaster since 1984 when 27 were killed by a fire at Emery Mining's mine in Orangeville, Utah.
It is understood the miners were leaving on a vehicle which takes them in and out of the mine's long shaft when a crew ahead of them felt a blast of air and went back to investigate, Mr Stricklin said.
They found nine workers, seven of whom were dead. Others were hurt or missing about a mile and a half (2.4km) inside the mine.