The search for six missing miners moved toward the back of the mine Tuesday, as officials hoped the men sought refuge in search of an air pocket, the Associated Press reports.

More than a week after the Crandall Canyon mine collapse in Huntington, Utah, crews were drilling another hole in hopes of finding the men. Two holes have already been drilled and a camera fitted down one of them, but the coal miners' fate is still unknown.

The camera's images revealed one indication of a miner's presence: a tool bag hanging from a post, 3.4 miles from the entrance and more than 1,800 feet underground.

"It indicates we're very close to where the miners were working," said Bob Murray, chief of Murray Energy Corp., co-owner and operator of the mine.

The collapse of the mine's midsection was thought to have pushed ventilated air into a pocket at the rear of the mine, where the miners may have fled when their escape routes were cut off by rubble, said Richard Stickler, chief of the Mine Safety and Health Administration.

Murray said the pace of rescue efforts picked up inside the mine, where heavy machinery was clawing at loose rubble that nearly fills a main passageway.

Rescuers cleared about 680 feet of the 2,000 feet of rubble they expected to encounter in the mine's main passageway.

The effort could take several more days, but for the first time since the Aug. 6 collapse, the rescuers were progressing steadily forward, without the frequent interruptions that have characterized the rescue effort so far, according to AP.