The FBI said today it is investigating the Belvoir Restaurant near here and its owner, Roy E. McKoy, because of reports that McKoy refused to serve a Washington television crew that included two blacks.

McKoy, 60, was jailed by federal officials in 1967 and 1974 for defying federal court orders to allow blacks to eat at his restaurant. He is under a permanent federal order directing him to comply with the 1964 Civil Rights Act and serve blacks, according to Virginia law enforcement officials.

Steven Pomerantz, assistant special agent in charge of the FBI's Alexandria field office, said, "Right now we're trying to verify" the late October incident, which he said the agency learned about from news reports. "We are giving the investigation priority attention, as we do with all civil rights matters, and we expect to bring it to a conclusion as rapidly as possible," he said.

Pomerantz said no agents have visited the restaurant yet, and that results of the investigation would be turned over to the Justice Department for action if it is warranted.

A Justice Department spokesman said yesterday that records of the 1967 order were being retrieved from storage for examination to see if McKoy's conduct has violated it. Pomerantz said the FBI began its investigation independently of the Justice Department.

Both local and federal officials said they have had no formal complaints against the establishment since 1974.

A three-member WRC-TV (Channel 4) television crew, in Fauquier County reporting a story on a local congressional race, stopped at the Belvoir Restaurant Oct. 30, and was told coffee would cost "$500 a cup," according to reporter Jim Upshaw, a member of the crew.

Upshaw, who is white, said he was contacted about the incident by FBI agents today and he told them McKoy made it clear he would not serve blacks.

He said he did not know if the black members of his crew, Eugene Givens and Tommy Childs, had been interviewed.

Yesterday, four black women from Dale City who learned of Upshaw's experience went to the restaurant, 50 miles west of Washington on Rte. 55, to have lunch, but McKoy had closed for the day.

At one point, he emerged from the house in back of his restaurant with a stick and ordered two deputy sheriffs off his property.

Today, the doors of the restaurant, which is also McKoy's home, remained locked, but around lunch time several people who drove into its parking lot were admitted. Smoke redolent of cooking food came out of the restaurant's chimney.

Sgt. P.F. Mercer of the Fauquier County's Sheriff's Department stood watch over the restaurant most of the day as a parade of newspaper and television reporters and photographers and curiosity seekers arrived.

"There were two cars parked outside at lunch," said Mercer. "He McKoy appears to be selectively allowing people in, if he knows them." Mercer said all those who entered the restaurant were white.

McKoy could not be reached to answer a reporter's questions today, and a woman who answered a telephone in the restaurant hung up immediately when asked to put McKoy on the phone.

Fauquier County prosecutor Charles Foley said selective service at a restaurant "is probably not appropriate behavior, but that would be very difficult to establish," and would depend on whether the people ate, whether they were friends of McKoy and whether they paid for their food.

McKoy's standoff with the four civil rights activists yesterday set this town abuzz today.

Many townspeople said they felt McKoy should simply be left alone. "None of the local people complain at all. There are plenty of other places to eat," said one woman.

Several local blacks said they simply avoid the Belvoir Restaurant.