MONTCOAL, W.Va. -- Two full days after the worst U.S. mining disaster in a generation, dangerous gases underground prevented rescuers late Wednesday from venturing into the Upper Big Branch coal mine to search for any survivors of the explosion that killed at least 25 workers.
Crews drilled holes deep into the ground to release the gases. By evening, a federal safety official said the levels of lethal carbon monoxide and highly explosive hydrogen and methane measured at the top of the holes were steadily dropping. Officials by late evening planned to test levels at the bottom of the holes to determine if three teams of five rescuers each can enter.
"We just can't take any chances" with the lives of rescuers, Kevin Stricklin of the federal Mine Safety and Health Administration had said earlier. "If we're going to send a rescue team, we have to say it's safe for them to go in there."
Officials could not say specifically when rescuers might be able to go in, but if the readings at the bottom were good, they want them on the move as soon as possible, Stricklin said.
Stricklin said relatives of the miners backed the decision to hold off for now.
"We've asked the families to be patient," he said earlier in the day.
Gov. Joe Manchin and others saw only a "sliver of hope" that the miners survived by reaching one of the shaft's rescue chambers, which are stocked with food, water and enough oxygen to last four days. Workers planned to drill another hole so they could lower a camera into one of the airtight chambers to see if anyone managed to get inside.
"We've been working against long odds from day one," Manchin warned.
The federal mine agency appointed a team of investigators to look into the blast.