Rescue crews continue to drill a small hole deep into a Utah mine in the hopes of establishing contact with six trapped workers.
One the drill reaches its target, a listening device will be sent down the 6.4 centimetre-wide hole, emitting a beeping sound so the miners will be able to find it in the dark.
"We may get no noise," Bob Murray, co-owner of the mine, told The Associated Press. "They may be dead."
The drilling could finish early Friday morning, but it will take an additional two hours to set up the listening device.
At first, the men were believed to be buried about 455 metres below the surface in central Utah, where they became trapped after a cave-in at the Crandall Canyon mine on Monday.
However, partly through the day rescue teams realized they would need to drill almost 580 metres because of the rough, uneven terrain in their way.
"It's not an operational problem. It's a time setback," said Allyn Davis, who oversees Western operations for the Mine Safety and Health Administration.
It's not yet known if the miners are alive or dead, but mining officials have said the workers could potentially survive in the mine for several weeks.
Rescue teams are also creating a larger 23-centimetre-wide hole that could enable them to drop down food and supplies to any survivors.
"We will put cameras down. We will provide communication. We will provide food. We could keep them alive indefinitely," said Murray.
It's hoped the workers can be reached in about a week.
Rob Moore, vice-president of Murray Energy Corp. and part owner of the mine, admitted there was potential for equipment breakdowns and dangerous ground shifts.
"Obviously we're dealing with the unknown," Moore said.
Several hundred people filled bleachers at the rodeo grounds Wednesday night for a candlelight vigil in the nearby town of Huntington. Men and women wiped away tears as Baptist pastor Sam Wilbanks prayed for the miners' safe return.
"Lord, I just pray again for these men that are in that old dark coal. Lord, I just pray tonight that the light of Jesus Christ might shine there tonight and they might know with all their heart that you are there with them," he said.
The audience lit candles one by one and placed them in the stadium dirt, spelling out the word "hope."
Relatives of the trapped miners have been receiving private briefings on the rescue effort by Murray. He said he took two relatives of the trapped miners on an underground tour Wednesday.
Maria Buenrostro, the sister of trapped miner Manuel Sanchez, said Murray became angry with the line of questioning from relatives when they met in the nearby town of Huntington on Wednesday. She said he walked out at one point.
Buenrostro also said there was no interpreter for three Spanish-speaking families.
"We want the truth, that's all we want," said Buenrostro, 40. "If there's nothing that they can do about it, you know, just tell us so we know what to expect when they bring them out."
Murray later said the families had thanked him.
"You can't make everybody happy," he said. "In a trauma like this, as the days wear on, tensions become more and more. I have been truthful with them."
With files from The Associated Press
