Rescuers hopeful despite no word from Utah miners

HUNTINGTON, Utah, Aug 10 (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 US mine safety official said today.

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.

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 today or early tomorrow.

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.

Robert Murray, chairman of Murray Energy, said earlier today that it would take at least another four to five days to clear the fallen rock and coal and reach the miners with an opening large enough to pull them to safety.

Officials say the men could potentially survive for weeks in an underground chamber if they were not killed by the initial collapse.

Murray has insisted that an earthquake triggered the mine's collapse but geologists dispute that, saying that shaking recorded by their instruments was caused by the cave-in.

Controversy has also risen over reports that the miners were engaged in a dangerous operation called ''retreat mining'' when the shaft collapsed -- though Murray has denied that such a technique was being used.

Retreat mining involves supporting the mine's roof with a column of coal, then removing those pillars and allowing the shaft to collapse as miners move to safety.

The Crandall Canyon Mine is on a high desert plateau some 140 miles (225 km) south of Salt Lake City, in what is known as Utah's ''castle country'' because of the towering rock spires that dot the bleak landscape.

REUTERS AE RN2354