A dispute between the owner of the Sago Mine and the United Mine Workers has led both sides to refrain from sitting in on interviews by state and federal officials investigating this month's fatal explosion at the coal mine.

A union official said neither its representatives nor those of International Coal Group Inc. attended interview sessions Thursday, a day after the company challenged the union's right to take part in the investigation involving a nonunion mine.

Several miners have asked the union to serve as their representative during the investigation, and federal investigators have officially recognized the union as the miners' representative.

The union and the company drafted a written agreement that says neither will participate in the interviews but the union has not approved it, said Phil Smith, the union's director of communications.

"We are still evaluating the language and have not officially agreed to it at this point," Smith said Thursday afternoon. "The hearings are proceeding. That really is the important thing."

Investigators are trying to determine the cause of the Jan. 2 explosion, which resulted in the deaths of 12 members of a 13-man mine crew. Survivor Randal McCloy Jr., 26, continues to improve and remains in a "light coma" at West Virginia University's Ruby Memorial Hospital in Morgantown.

Democratic Gov. Joe Manchin and Rep. Shelley Moore Capito, R-W.Va., said the union had a right to be at the interviews.

Manchin told reporters Thursday that his office stepped in Wednesday after the company objected to the union's presence.

"The union should be there. They have the experts. It was their rescue teams that were out there risking their lives every minute I saw," he said.

Rescue teams from both union and nonunion mines helped at the Sago mine.

Capito also announced a $535,860 federal grant to provide safety training and retraining for miners across West Virginia. The grant is part of a federal Mine Safety and Health Administration program that is providing $4 million to 20 states for miner safety programs.

Manchin on Thursday called for several improvements to coal mine safety, including oxygen stations, wireless communication with miners and emergency locator transmitters.

The governor said full-time rescuers should augment the current volunteer force and that rescue equipment, which he said in some cases is 40 to 50 years old, should be upgraded.

Manchin has no immediate plans to introduce mine safety legislation during the current legislative session, said his spokeswoman, Lara Ramsburg. The state plans public hearings on the disaster this spring.

"We are waiting for the investigation to run its course. It's through the investigation we will get the facts about where things can be improved," Ramsburg said.