MONTCOAL, W.Va. -- High levels of dangerous methane gas made it impossible for rescuers to venture inside a coal mine Wednesday to search for survivors of an explosion that killed 25 workers.
Crews drilled holes to release the gas, but by late afternoon the levels remained far too high for searchers to safely enter the Upper Big Branch mine to look for four people missing in the worst U.S. mining accident in more than two decades. They could not say when they might be able to go in.
Workers wanted to drill another hole so they could lower a camera into an airtight rescue chamber to see if anyone had managed to get inside, Kevin Stricklin of the Mine Safety and Health Administration said at a briefing Wednesday.
''If we're going to send a rescue team, we have to say it's safe for them to go in there,'' Stricklin said. ''We want the air to be clear enough to let them go without being in smoke.''
The disaster has brought new scrutiny for mine owner Massey Energy Co., which has been repeatedly cited for problems with the system that ventilates explosive methane gas and for allowing combustible dust to build up. The federal mine agency on Wednesday appointed a special team of investigators to look into the blast, which officials said may have been caused by a buildup of methane.
Like many other mine operators, Massey frequently sidesteps hefty fines by aggressively appealing safety violations at the mine, according to an Associated Press analysis of mine safety records.
Rescuers hoped the four miners might somehow have reached a chamber where they could survive for four days, though they acknowledged the odds were against them. Rescuers banged on a drill pipe for about 15 minutes after the first hole was complete but got no response.
''We've been working against long odds from day one,'' Gov. Joe Manchin said at a briefing Wednesday afternoon.
Family members could do little but wait.
Alice Peters said she was told her 47-year-old son-in-law, Dean Jones, was among the missing, though Massey said Wednesday it does not know which four miners might be alive.
Seven bodies were pulled out after the explosion, and two miners were hospitalized. Manchin said Wednesday that one was doing well and the other was in intensive care. Eighteen bodies remained in the mine, but emergency workers were only able to identify four before methane forced them out Monday.