U.S. Park Police, after searching the murky Potomac for three persons believed to have been in a white Chevy that rolled into the river, said yesterday the dunking apparently was the work of vandals.

"We think the car was stolen or abandoned," said Sandra Alley of the Park Service. "One witness said he saw people near the car when it went in, but it looks like nobody went in with it."

Police called off their search yesterday afternoon, after divers from several jurisdictions had combed the floor of the Potomac near the Woodrow Wilson Bridge off Alexandria.

The car, a 1977 Chevrolet Nova, which was recovered without license plates or registration papers, apparently plunged into the river at about 10 p.m. Tuesday after it crashed through the sea wall at Jones Point Park.

Alexandria has one of the highest rates of auto theft in the Washington region, according to the city police department, and police said this car might have been taken for a joy ride and then spontaneously dumped in the Potomac.

The park police said their search began after witnesses reported that three cars entered the park together along a road just north of the bridge. According to police, the witnesses said two of the cars stopped near the water's edge and the driver of the third car revved its engine and escaped before the car hit the water.

One witness interviewed at the park Tuesday night said he believed there were three people in the car when it went into the water.

Police were trying yesterday to trace the history of the car through its vehicle identification number and three stickers attached to its windows: one from the Navy's Suitland installation; a Fort Stewart, Ga., Department of Defense decal and a green Maryland-National Capital Park and Planning Commission sticker.

Alexandria firefighters were the first officers on the scene Tuesday night, minutes after they received the report of a vehicle in the river.

"We have no suspects, but we are investigating the incident as closely as we can," Alley said. "To my knowledge this is the first time we have ever had a report of this kind. I don't think it's much of a prank."