The prospects that the miners would still be alive appeared bleak after holes bored into the mine shaft revealed carbon monoxide levels three times higher than people could withstand. Carbon monoxide, a byproduct of combustion, can be lethal.
A camera lowered into the hole also showed no signs of life.
"With each hour that passes, the likelihood of a successful outcome diminishes," said Ben Hatfield, chief executive of mine owner International Coal Group Inc., according to the Associated Press.
The men are trapped 260 feet underground in the Sago Mine and are believed to be about 12,000 feet past the opening of the shaft. By early evening, the rescue teams had burrowed 11,400 feet. They were working their way down on foot for fear machinery might cause volatile gases to explode, the AP reported.
President Bush said the nation was praying for the miners, and he offered federal aid to get the men out alive.
"May God bless those who are trapped below the earth," he said.
Hatfield said it was possible the men barricaded themselves in another part of the mine and were still alive. But, "we are very discouraged by the results of this (air quality) test," he said.
A camera lowered into the 6 1/4-inch hole spotted no sign of the trapped men. Drilling crews pounded on a steel pipe and listened for a response but heard nothing.
"Obviously, it was devastating," said Nick Helms, whose 50-year-old father Terry was among the missing, of the test result. He expressed optimism that the miners could still be alive in a part of the mine with safer air.
"My father and every person who goes into that mine knows what they're doing. I'm sure they found a way to stay safe," he said, quoted the AP. "I just want to see him again."