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TALLMANSVILLE, W.Va. (AP) - Rescue crews scrapped their conservative approach to free 13 trapped miners Tuesday after efforts to contact the men went unanswered and air samples showed continued high levels of contaminated air.

"We determined with the cooperation of state and federal agencies that we can move forward and at a quicker pace and do it safely," said Ben Hatfield, chief executive officer of mine owner International Coal Group Inc. of Ashland, Ky. "We believe we were overly conservative before." Hatfield said tests found that carbon monoxide levels far exceed federal regulatory limits in the Sago Mine. He made the comments after rescuers trying to reach the trapped miners successfully punched a hole into the mine early Tuesday.

A camera was inserted into the 6 1/4 inch hole to look for signs of life. Drilling crews pounded on steel pipe and listened for a response in the section of the mine where the trapped miners were believed to be located, Hatfield said. "They repeated this process several times over a 10 minute period but the drill crew heard no response," Hatfield said.

Air monitors inserted into the mine found high concentrations of carbon monoxide. Carbon monoxide levels measured 1,300 parts per million, exceeding the 400 parts per million maximum level that sustains life, Hatfield said. "Therefore we are very discouraged by the results of this test," Hatfield said.

The camera search of the area proved inconclusive, and evidence of extensive damage was not seen. "No barricades or survivors were seen," he said. Still, Hatfield said the trapped miners could still be alive. "They could be in another location or they could be barricaded somewhere," Hatfield said.

Hatfield said officials abandoned plans to move in a camera-equipped track-mounted robot with sensors to measure air quality, saying that without the robot "we can move forward and at a quicker pace and do it safely." The robot had become bogged down in mud inside the mine.

Family members, who had been optimistic and talkative with reporters, earlier retreated to the nearby Sago Baptist Church without making any comments. Rescuers had penetrated 10,200 feet into the mine. The trapped miners are believed about 12,000 feet into the mine.

"We will push forward as quickly as we can as long as there is a shred of hope that we can get our people out safely," Hatfield said. Gov. Joe Manchin said West Virginians "believe in miracles." "We still pray for miracles in West Virginia," Manchin said. "There is still a chance and there's hope and we have that."