San Juan de Sabinas, Mexico ? More than three days of backbreaking labor brought rescuers close to the site where two of 65 trapped coal miners are believed to be located, a federal official said Wednesday.

Whether the two men are dead or alive could provide a clue to the fate of workers deeper inside the Pasta de Conchos mine, said federal Labor Secretary Francisco Salazar.

“These two people will give us an indication of what it is that could have happened,” Salazar told a television network.

Salazar said the two conveyor belt operators are believed to be less than 54 yards past a wall of debris that rescuers have been trying to break through since early Tuesday. The miners were trapped by an underground gas explosion early Sunday.

Mine administrator Ruben Escudero told family members that workers had been able to pump additional fresh air into the mine, possibly allowing rescuers to shed their oxygen tanks and work faster without the extra weight.

Ervey Flores Moreno, center, a miner who was injured in Sunday's explosion, talks to the media Wednesday after being released from the hospital.

Because of fears that machinery could spark explosions, rescuers wearing gas masks and tanks have had to move tons of fallen dirt, rock, wood and metal with picks and shovels.

They got through a wall of debris, only to encounter another 600 yards inside the tunnel early Tuesday. While the two conveyer belt operators may be just beyond the second wall, most of the others are thought to be as far as three miles from the mine’s entrance.

Mine operators have said each of the 65 men was carrying a tank with only six hours of oxygen supply. They also said there were oxygen tanks scattered throughout the mine.