An underground explosion ripped through a coal mine shaft deep in the Appalachian Mountains of southwest Virginia Tuesday night, killing seven miners in an accident federal officials yesterday called the worst mining disaster in Virginia in 25 years.

Three miners suffered serious burns and were hospitalized as a result of the explosion that occurred at 10:15 p.m. at Clinchfield Coal's No. 1 mine in McClure, a hamlet of 300 located 20 miles from the Kentucky border.

A team of federal and state mine inspectors was dispatched to the accident site nearly 400 miles southwest of Washington to investigate the accident in the three-year-old mine.

United Mine Workers President Rich Trumka also toured the mine, one of the largest in Virginia. Federal records show the mine has been cited for at least 163 health and safety violations since October 1982. Those violations include inadequate ventilation and deficient roof supports.

"Their injury rate is obviously above the national average for coal mines, and there were probably more citations per inspection than the national average and more citations at that mine in recent months," said John McGrath, a spokesman for the Federal Mine Safety and Health Administration. Last February a miner was killed when a portion of the roof caved in.

In fact, McGrath said, a federal inspector had visited the mine Tuesday for a spot inspection that is required every five days because the mine emits large amounts of potentially explosive methane gas.

"It's true that the first part of this year we have had a relatively high number of citations," said Susan Copeland, a spokesman for Clinchfield Coal, a subsidiary of the Pittston Group, one of the nation's largest coal operators. "However, this is one of the largest mines in Virginia and has an unusually high inspection rate. In terms of safety we feel this is a well-run mine."

Federal authorities cautioned that it would probably be days before they determined precisely what caused the explosion in the shaft more than 400 feet underground. But company and United Mine Workers officials speculated that a spark or coal dust may have ignited the gas causing the accident.

It is the nation's worst coalfield disaster since January 1982, when seven miners, four of them members of the same family, were killed in an explosion in Craynor, Ky.

Federal records show that Clinchfield is a "hot" or gassy mine, because it emits more than 3.2 million cubic feet of methane gas daily. That fact, according to John Kennedy, president of United Mine Workers Local 28, is never far from a miner's consciousness.

"It's a hot mine and any spark, like from someone pounding a hammer, could have touched it off," he said. "It's something that you're constantly aware of. You just always have to watch for ventilation."

Although the explosion occurred shortly before the end of the "hoot owl" 3 to 11 p.m. shift, it took rescuers more than seven hours to recover the bodies of the dead, which were clustered in one section of the mine.

"There was no sound of any explosion, it was just pressure," said Teddy Crihfield, 24, who was working in another part of the mine and was one of 74 who escaped uninjured. "The pressure knocked me down . . . . It was like something being forced between your ears . . . . My ears were still ringing this morning."

Residents said yesterday the first sign they had that anything was wrong was when workers arriving for the 11 p.m. shift were prevented from entering the mine. They were joined by miners' families who learned there had been an accident and gathered at the crossroads outside the entrance to the mine.

Several hours later, a Virginia state police official read the names of seven miners over a loudspeaker and asked that relatives meet company officials inside an office. There they were informed of the deaths.

"It's just something, you know, that's unbelievable, like a dream, until it happens to you," said Daisy Skeens, whose 36-year-old brother-in-law Luther McCoy, a 17-year veteran of the mines, was among the dead.

Friday was to have been foreman F.C. Riner's last day with Clinchfield Coal, according to his daughter Connie Riner. "He dreaded retirement," she said, and had originally been scheduled to retire May 25, but rescheduled his last day for tomorrow, the beginning of the annual two-week nationwide miners' vacation.

"He didn't have to be underground at all," said Riner, "but he wanted to spend the last (week) on the job with his men." Riner said her father, who was 58, frequently discussed the hazards of his job. "He knew the mine was dangerous, he told us it was ready to blow. He told us in detail what would happen in an explosion . . . he told us how hot it would get. He said, 'If it blows, don't expect to find me.' "

Also killed was Mary Kay (Cat) Counts, 51, a shuttle car operator and the first woman killed in a mining disaster in Virginia. "Cat went right down there like everybody else," said Joe Lee Baker, an ex-miner who owns the weekly Cumberland Times.

"She called herself 'Mom' and called everybody else 'Darlin,' " said Crihfield.

Tuesday's accident was another harsh blow to Virginia's economically devastated coal-mining region, towns like McClure where small frame houses line the railroad tracks and where unemployment has been running more than 20 percent.

"When a disaster like this strikes in a county of small towns, everyone feels grief and compassion," said Mackie Rose, chief of the local volunteer fire department and a miner. "Some of our rescue workers, it was their first mining accident, they sat down and cried. People's dads, husbands, brothers work in the mines. That's all we have. That's what we work at."