HUNTINGTON, Utah (AP) – Teams of rescuers struggled to clear fallen rock from tunnels early Tuesday, trying to reach six coal miners trapped by a cave-in more than 1,500 feet below the surface.

With no word on whether the six were still alive, crews worked through the night in shifts, with teams coming and going along the road leading to the Crandall Canyon mine in a forested canyon.

“Right now I can’t say if it’s looking any better,” weary miner Leland Lobato said. “They’re doing what they can to keep everybody as fresh as possible so nobody gets tired.”

Several other miners emerged with blackened cheeks after an all-night shift.

The trapped miners were believed to have been in a chamber 3.4 miles inside the Crandall Canyon mine. Rescuers were able to reach a point about 1,700 feet from that point before being blocked by debris.

Emery County Sheriff Lamar Guymon said at least 100 people were working on the rescue effort Tuesday morning. He said he expected the mine company to begin bulldozing a road needed to bring in a drilling rig.

The rig could punch holes in the mine to improve ventilation and determine if the miners survived, Robert E. Murray, chairman of Murray Energy Corp. of Cleveland, a part owner of the Crandall Canyon mine, said Monday.

Federal mine-safety inspectors, who have issued more than 300 citations against the mine since January 2004, were helping oversee the search.

If they are alive, the miners would have plenty of air because oxygen naturally leaks into the mine, Murray said. The mine also is stocked with drinking water. If rescuers can open an old mine shaft, they think they can get within 100 feet of where the men were believed to be, Mr. Murray said.

The mine uses a method called “retreat mining,” in which miners initially leave pillars of coal to hold up an area of the mine’s roof. When an area is mined out, the company pulls the pillar and recovers that coal, allowing the roof to collapse. Experts say the technique is one of the most dangerous in mining.

Many of the family members don’t speak English, so Huntington Mayor Hilary Gordon said she hugged them, put her hands over her heart and then clasped them together to let them know she was praying for them, she said.

“Past experience tells us these things don’t go very well,” said Mrs. Gordon, whose husband is a former miner.

Still, the families “seem to have a quiet determination at this point,” she told Fox News on Tuesday morning.

Outside the senior center, Ariana Sanchez, 16, said her father Manuel Sanchez, 42, was among the trapped miners. She said she cried when her mother told her the news, and declined to say more.

Other than Mr. Sanchez, little was known about the six miners, but Mexico’s consul in Salt Lake City, Salvador Jimenez, said Tuesday that three of the men are Mexican citizens.

Mr. Jimenez said, however, that he did not know any details about the men, including whether they are U.S. residents, their ages or hometowns.

The sheriff said 90 percent of the community is tied to coal mining or energy production. “This affects everybody, not just six families,” he said.

The mine is built into a mountain in the rugged Manti-La Sal National Forest, 140 miles south of Salt Lake City, in a sparsely populated area.

University of Utah seismograph stations recorded seismic waves of 3.9 magnitude early Monday in the area of the mine, causing speculation that a minor earthquake had caused the cave-in. Scientists later said the collapse at the mine had caused the vibrations. But later, they said a natural earthquake could not be ruled out and more information was needed to conclusively determine what happened.

Government mine inspectors have issued 325 citations against the mine since January 2004, according to an analysis of federal Mine Safety and Health Administration online records. Of those, 116 were what the government considered “significant and substantial,” meaning they are likely to cause injury.

Having 325 safety violations is not unusual, said J. Davitt McAteer, former head of the MSHA and now vice president of Wheeling Jesuit University in West Virginia. “It’s not perfect but it’s certainly not bad.”

This year, inspectors have issued 32 citations against the mine, 14 of them considered significant. Last month, inspectors cited the mine for violating a rule requiring that at least two separate passageways be designated for escape in an emergency.

It was the third time in less than two years that the mine had been cited for the same problem, according to MSHA records. In 2005, MSHA ordered the mine owners to pay $963 for not having such escape routes. The 2006 fine for the same problem was just $60.

Overall, the federal government has ordered the mine owner to pay nearly $152,000 in penalties for its 325 violations, with many citations having no fines calculated yet. Since January, the mine owner has paid $130,678 in fines, according to MSHA records.

Asked about safety, Mr. Murray told reporters: “I believe we run a very safe coal mine. We’ve had an excellent record.”

Utah ranked 12th in coal production in 2006. It had 13 underground coal mines in 2005, the most recent statistics available, according to the Utah Geological Survey.

Last summer, Congress tried to make coal mining safer, assessing hefty fines for rule violations and requiring more oxygen to be stored underground.

The changes were in response to the Sago mine disaster that killed 12 miners in West Virginia.

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Associated Press writers Garance Burke in Huntington; Brock Vergakis in Salt Lake City; and Seth Borenstein in Washington, D.C., contributed to this report.