Charleston, N.C. ? Federal investigators entered the Sago Mine on Saturday for the first time since the bodies of 12 miners were removed earlier this month.

It likely will be another week before they can reach the deepest parts of the mine to investigate what caused the Jan. 2 explosion that had trapped the men deep underground, International Coal Group President Ben Hatfield told The Associated Press.

The mine has been completely idled and all power disconnected since Jan. 4. Because potential dangers remain, a special mine team began the slow process of restarting water pumps and repairing damaged ventilation systems, Hatfield said.

“What we’re essentially doing is reopening the mine in a very cautious manner,” he said. Still, “we’re that much closer to getting answers.”

The company has said the explosion occurred in an area of the mine that had been sealed in December. Only one man survived the blast and subsequent carbon monoxide poisoning. Randal McCloy Jr., 26, of Simpson, remained in a light coma Saturday.

Hatfield also said his company received a signed petition from nearly 60 percent of its work force rejecting help from the United Mine Workers of America. Instead, they named three co-workers to represent them during the investigation.

Sago is a nonunion mine, but the union said on Tuesday that several employees had designated UMW as their representative. UMW spokesman Phil Smith could not immediately be reached for comment Saturday.