Rescue teams were still racing to reach six coal miners who remained trapped 1,500 feet below ground a day after an Aug. 6 collapse at the Crandall Canyon Mine in central Utah.

The collapse was so intense that it initially registered as a magnitude 3.9 earthquake, according to researchers at the University of Utah who oversee seismography readings for the U.S. Geological Survey.

The U.S. Department of Labor’s Mine Safety and Health Administration was coordinating the rescue with local mine company officials.

Rescuers brought in heavy drilling equipment Aug. 7 to try to reach the miners, an effort that the mine’s owner said would take at least three days.

“Progress has been too slow, too slow,” Robert E. Murray, chairman of Murray Energy Corp. of Ohio, told the press. His company owns the Crandall Canyon Mine.

Unfortunately for the miners and their families, his comments were in line with the company’s prior performance on worker safety issues.

Federal mine safety inspectors have issued more than 300 citations against the mine company since January 2004.

The Crandall Canyon 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 a section 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.

A picture of the company’s exploitation of Mexican workers to do this dangerous work is starting to emerge. Mexico’s consul in Salt Lake City, Salvador Jiminez, said Aug. 6 that three of the trapped miners are Mexican citizens. He told the press that he did not know any details about the men, including whether they are U.S. residents, their ages or their hometowns.

Of the citations issued against the company since 2004, 116 were “significant and substantial and likely to cause injury’” according to the U.S. government’s online records.

News reports indicated that the rescue was delayed because there was no second passageway for escape. Last month the mine owners were cited for that violation for the second year in a row. The Bush-appointed safety board fined them only $60, according to Mine Safety and Health Administration records.