Bob Murray, part owner of the Crandall Mine, sits with a hand on his head during the afternoon news conference about the six miners trapped in the mine, on Thursday, near Huntington, Utah.

HUNTINGTON, Utah (Reuters):

Rescuers have heard no signs of life from six miners trapped for five days in a Utah coal mine after sending down a microphone, but remain hopeful the men are alive, a U.S. mine safety official said yesterday.

Richard Stickler, head of the Mine Safety and Health Administration, said the 1,800-foot (550-metre)-deep bore hole through which the microphone was lowered may have missed the area of the mine where the men were believed to be.

"At this point, the thing to do is continue on our plan, maintain our hope," he told a news conference.

The six men have not been heard from since Monday when part of the Crandall Canyon Mine near Huntington, Utah, collapsed.

Rescue crews have removed the microphone and will lower a survey instrument to pinpoint the drill hole's location in the mine, Stickler said.

Initial tests taken through the 2-1/2-inch (5-cm) bore hole of the air in the mine showed it could sustain life but later readings indicated lower oxygen levels, suggesting they may have hit a sealed-off area of the mine and not the area they had intended to reach, he said.

larger hole

A second, 9-inch (23-cm) hole that will enable rescuers to lower a camera into the mine - and could provide a way to give the miners air, food and water if they are still alive - is still being drilled, but officials would not say when they expected it to be completed.

Officials earlier had said they expected the larger hole to punch through into the mine late yesterday or early today.

Rob Moore, vice-president of mine co-owner Murray Energy, said directional drilling devices used on the 9-inch hole gave it a better chance of hitting its target.

AP