Sago Mine survivor Randal McCloy Jr. appears to be awakening from his coma, and his improving condition may allow him to be transferred to a rehabilitation center within a few weeks, doctors said Wednesday.

McCloy, 26, has been breathing on his own for days and is opening his eyes, said Dr. Julian Bailes of West Virginia University's Ruby Memorial Hospital, adding that he "has purposeful movement" and "is responding to his family in slight ways."

Bailes said doctors now consider McCloy to be in a "light coma."

McCloy is believed to have suffered brain damage from lack of oxygen, but the extent of the damage is not yet known.

Because of the amount of time he spent in the mine before being rescued, "we are in many ways in uncharted territory with predicting his recovery," said Bailes, a neurosurgeon. "Many people with severe carbon monoxide poisoning end up with severe cognitive, personality, memory, visual and motor responses. We just don't know."

McCloy has been unconscious since he was pulled from the mine more than 41 hours after the Jan. 2 explosion that led to the deaths of 12 other miners. Officials have said one miner was apparently killed by the blast itself, and the others were asphyxiated.

McCloy was moved out of intensive care Tuesday but remains on dialysis because of kidney damage.

The cause of the mine explosion has still not been determined. One theory is that lightning hit an old well pipe, conveying electricity into the tunnels.

However, "it's very premature to speculate on any contribution that that may have had," Richard Gates, lead investigator for the federal Mine Safety and Health Administration, said Wednesday.

Water and poisonous gases are still being purged from the mine, about 100 miles north of Charleston, and Gates said federal investigators expect to gain access in a few days.

Federal and state regulators investigating the accident began interviewing witnesses Tuesday. Mine company officials also attended the interviews, along with representatives of a coal miners union.

Also Wednesday, the mine's owner, International Coal Group Inc., issued a statement objecting to the union's involvement. The Sago Mine is nonunion, but several miners asked the United Mine Workers of America to represent them during the investigation.

The union "seeks to interfere with the investigation in order to exploit the tragedy at the Sago Mine for their own purposes in an effort to revive organizing efforts that have floundered for more than a decade," the company said.

But union President Cecil Roberts defended the union's involvement. "This investigation is about finding out the truth," he said. "If the company has nothing to hide, it should favor an open investigation with all parties participating fully."

He also said the employees who sought union representation would remain anonymous, despite what he said were attempts by the coal company to learn their names. "MSHA did not release their identities, nor will we," he said.

MSHA also announced Wednesday that it will conduct an internal review of its oversight of the Sago Mine.