A Fairfax City couple and the wife's visiting parents from England were killed yesterday in an early morning fire of undetermined origin that spread from the basement of their town house to the second floor bedrooms, where they were sleeping, a fire official reported.

The victim of the fire at 10465 Courthouse Dr. were identified as Ronald Grover, 40 and his wife, Pamela, 43 and Mrs. Grover's parents, John and Winifred Jones, both 74, according to a fire department spokesman.

The cause of the blaze was still under investigation, but arson was not suspected, the spokesman said.

Neighbors said the Grovers had been living in the area for about six months. Grover was retired from the Marine Corps and worked as a security guard at the Annandale campus of the Northern Virginia Community College, neighbors said.

Mrs. Grover was an employee of the United Virginia Bank in Alexandria, they said.

The Joneses had been visiting the couple for about a week and were scheduled to leave for England today, according to William H. Contos, a next-door neighbor.

The Grovers have a 19-year-old son, Tommy, who was not at home when the fire was reported at 1:16 a.m., neighbors said.

According to a fire department spokesman, the blaze spread from the basement of the home to the first and second floors. It took the firemen 30 minutes to bring the fire under control, although they remained on the scene until 5:26 a.m.

Aldo F. Gonzalez, a next-door neighbor, said he was awakened by "firemen or police banging on my door."

When he and his family got outside, Gonzalez said, the smoke was coming from the front of the Grover home and "the back of the house was in flames."

Both of the adjoining town houses to the Grover home received some smoke damage.

Six companies and 30 firemen fought the early morning blaze, the fire department spokesman said. Damage to the house and contents was estimated at $75,000, he said.

One fireman, Ken Rhodes, was treated at Fairfax Hospital for burns on the neck and later released, the spokesman said. A Fairfax City patrolman, William O'Donnell, was treated at Commonwealths Doctors Hospital for ankle and back injuries he suffered when be slipped on ice, the spokesman said.