As rescue crews drilled to within a few hundred feet of the six miners trapped in Utah's Crandall Canyon mine, their families wait and worry.
"I'm just praying and hoping that they make contact," Lucile A. Erickson, the mother of Don L. Erickson, a longtime worker at the mine, told ABCNEWS.com. "He's a great person, good heart, he likes to fish and hunt."
Don Erickson, 50, a father of two sons and several stepchildren, was the boss of the crew that day because he had agreed to substitute for another worker, said his mother. "He kind of filled in for another guy who took off to take a class that day," she said.
Erickson never complained to his mother about conditions at the mine, despite some near cave-ins. She said that mine owner Bob Murray was talking to the families every day. Asked whether Murray had been a big source of support during this difficult time, she said, "No, but I don't want to get into it." She added that the authorities and rescue crews are "doing all they can."
ABC News has confirmed the identities of all six miners. In addition to Erickson, the other five are Manuel Sanchez, 42; Kerry Allred, 57; Brandon Phillips, 43; Carlos Payan, Luis Hernandez.
Sanchez, one of three Mexican nationals among the trapped miners, has three daughters and a son. The longtime miner's nephew Julio said that the family was waiting and hoping for the best. "I'm worried."
Raymond Rivas, 20, is friends with Sanchez's daughter, 16-year-old Arianna. "He's our next-door neighbor. He was a good guy, really nice, a good father. I only talked to him a few times. &133; He's worked at the mine for a long time."
Some of the Mexican nationals may be illegal immigrants, according to Barbara Stinson Lee, a spokeswoman for the Roman Catholic Diocese of Salt Lake City who talked to the Rocky Mountain News. She reportedly asked photographers not to take pictures of families who attended a Mass Tuesday night.
"It is a request from the families that there be no photographs. It's not grief. It's an immigration issue. They don't need pictures on the front page of newspapers," Lee told the News.
Yet mine owner Bob Murray insisted during an afternoon news conference that all of his employees were legal.
"I know that our company has never hired illegal aliens, ever, so I'm sure that these miners are totally here legally," he said. "I can say that I'm 100 percent certain that they're legal workers here because we screen them very carefully."
According to Lucile Erickson, the mine hired many of the Mexican workers who were left jobless when a nearby mine shut down recently.
Immigration advocates say that Mexican workers are increasingly taking jobs at mines in the United States, drawn by the high pay and better conditions.
"I wasn't surprised to see that half of the trapped miners were Mexican," said Arnoldo Garcia of the National Network of Immigrant and Refugee Rights. "Northern Mexico is famous for mining, and they are very skilled workers who are looking for better pay so they come here."
Hector Davila, a mine owner in northern Mexico, hasn't been able to reopen his two mines because so many skilled workers have gone across the border. "All of my miners went to the States," he said. "Whenever you're trying to hire 50 workers, you'd just put an ad in the newspaper, and you'd have 100 workers trying to fill those jobs. Now, you run the same ad and maybe one or five workers will come by."
Davila said that Mexican miners emigrate because American mines pay better and use newer equipment. Also, they tend to take more high-risk jobs at mines in general. "They will usually work in those mines that are more unsafe than others, and in those sections of the mine that are more dangerous," said Davila. "They don't mind as long as there's work. They'll take the jobs that other miners won't take."
Many Mexican immigrants work at mines that are not unionized, such as the Crandall Canyon mine, said Davila. Several years ago, the United Mine Workers attempted to organize 40 Mexican immigrants to negotiate with a nearby mine, C.W. Mining's Co-op Mine, but ultimately failed in the effort.
Meanwhile, questions remain as to whether the cave-in came during a dangerous retreat-mining, where pillars of coal are used to hold up the mine roof, then removed.
Murray has said that no retreat mining was under way at the time of the collapse.
But federal safety official told Reuters rescue efforts have been complicated by a mining method that left a great load of rock balanced on a few pillars.
"There's a pretty stiff sandstone formation above the coal mine…after the pressure builds up to a certain degree, then the pillars start failing," said Robert Friend, the deputy assistant secretary of the federal Mine Safety and Health Administration.