DANTE, VA., DEC. 28 -- High levels of explosive gas kept rescuers out of a coal mine today where a miner was sealed by an explosion Saturday, and family members gathered under overcast skies awaiting word of his fate.

Officials planned to drill a 400-foot hole into the mine to see if the explosive methane gas and carbon monoxide had subsided enough to resume the search for miner Ted Street. The hole could take until Tuesday morning to finish, said Mike Abbott, a spokesman for the mine division of the state Department of Mines, Minerals and Energy.

Chief mine inspector Harry Childress said Street was the only person in the Double R Coal Co.'s No. 2 mine when the explosion occurred. Officials said the gases and intense heat made it unlikely he could survive. "We can't really speculate on that," Abbott said. But he said that there were no indications that Street was alive, and emergency oxygen tanks located throughout mine shafts last for only about an hour.

At the mine in southern Dickenson County, state and federal rescue crews stood by waiting to be allowed back into the mine if the high levels of methane gas and carbon monoxide declined.

A ventilation fan was blowing in the mine, but officials worried that the explosion might have closed off ventilation passages and trapped some pockets of methane, which occurs naturally in and around coal seams.

"We have to assume after this explosion that the ventilation controls in the mine that had been established more than likely were knocked down or had been destroyed by the explosion," Abbott said from his office in Big Stone Gap.

Rescue attempts at the mine were hampered Sunday by fears of a second explosion after crews went 1,000 feet into the mine before they were brought back out.

Childress said officials were not sure what caused the explosion. The investigation was continuing, he said.

Double R Coal officials could not be reached at the mine office because the phone was knocked out in the blast.

"The force of the explosion shifted the mine office off its site," Abbott said. Mine owner Bill Ratliff was at the site and could not be reached, Abbott said.

Abbott said Street apparently had gone into the mine Saturday to get some coal for his house.

The Virginia mining industry has recorded its safest year in 1987, with one confirmed mining death, which occurred when a rock struck one of the owners of a small coal mine in Dickenson County. In 1986, 11 Virginia coal miners were killed; in 1985, eight died.