The remains of an explosive device that apparently detonated early Sunday near the Vienna police chief's unmarked car were discovered yesterday by a police captain.

No one was hurt by the explosion, but police summoned investigators from the Fairfax County Fire Department and the federal Bureau of Alcohol, Tobacco and Firearms to investigate.

Chief Daniel Boring, who heads the 39-member Vienna force, was out of town yesterday and at the time of the explosion, authorities said. His car was parked next to a brick wall behind Vienna police headquarters at 215 S. Center St.

Capt. Johnny T. Price said he noticed some damage to the car about 2 p.m. yesterday. "It was just a broken piece of plastic on the car," Price said. "Originally, I thought somebody had backed into a snowbank."

Price said whatever exploded was on the ground, not on the car.

Police began interviewing neighbors and determined that the explosion occurred between 2:30 and 3:30 a.m. Sunday. Investigators declined to say what type of device might have been used, and they were scouring the police parking lot last night for physical evidence.

Ed Raskind, who lives on the other side of the brick wall that borders the police parking lot, said he was doing laundry between 2 and 3 a.m. Sunday. At one point, he said, his "dogs started jumping up and down," but he didn't notice a loud noise. "It didn't sound like a boom," he said.

There were no obvious signs of an explosion in the parking lot, such as powder burns or debris, and nearby vegetation appeared undisturbed. Price said he could not think of a reason Vienna police might be targeted for an attack, and he asked anyone with information to call either the Vienna police or the Fairfax fire marshal's office.