A Montgomery County truck driver who at first was believed to have been killed in a fiery truck accident in Virginia has been declared a missing person and authorities are expected to list the fire as arson.

Roman Leimer, 39, an Exxon truck driver and wine importer, was believed dead until a Smithsonian Institution anthropologist, called into the case by Virginia authorities, ruled last week that the bones and flesh found in the wreck were not Leimer's, but were those of a pig.

David Crump, the Warren County, Va., prosecutor, said yesterday that Leimer now is considered a "missing person." State police sources said Crump also will soon declare that the 8,900-gallon Exxon gasoline tanker that Leimer had been driving Jan. 13 was set on fire deliberately. The tanker, valued at $100,000, was found ablaze on I-66 about two miles west of Front Royal, Va., at the foot of a 35-foot embankment.

Crump said yesterday that arson investigators had determined that "there was no human being in the truck" when the fire occurred.

According to informed sources, investigators have concluded that the tanker had been driven off the shoulder of the road to a point about 35-feet below, where the truck stood upright. The fire reportedly burned from the front end of the 45-foot trailer toward the rear, and no explosions occurred. The engine transmission was left intact.

The only remains found were three bones covered with charred flesh, and a wristwatch, according to police. A tow truck operator and a member of the rescue squad also said that they saw a pair of men's shoes on the side of the road where the truck was ablaze.

A Virginia state trooper saw the tanker parked on the side of the road about 15 minutes before the fire. The Austrian-born Leimer was smoking a cigarette nearby and told the officer that he was taking a rest because he was drowsy.

Crump confirmed this week that before talking to Leimer, Trooper Ronkeith Kurtley stopped to check on a small, blue car parked on the shoulder of the road about half a mile behind the tanker. The driver of the car, a blond woman with a German accent, said she had stopped because she was tired. Police are looking for the woman.

Leimer had reserved four plane tickets to fly to West Germany on Jan. 22, according to police, but the tickets were not purchased. His passport was found at home.

At the time of the truck fire, Leimer was threatened by mounting debts and lawsuits connected to a fledgling wine distributing business he had launched two years ago.

Leimer's wife and three children, who live in Burtonsville, have refused to comment on the circumstances of his disappearance. The family held a memorial service for Leimer several days after the accident.