When she stopped the 1986 Chevrolet with Florida plates for speeding in Stafford County Wednesday night, State Trooper Deborah D. King had a feeling that something more was going on.

"The gentleman was nervous," King said yesterday. "He was inconsistent. Each time I asked him something, his answer changed slightly. He had this attitude."

When she asked the driver if he would allow her to search the car and he refused, King called for state drug agents to follow him. Two counties and six hours later, at about 3 a.m. yesterday, a K-9 team on loan from the D.C. police smelled trouble in the trunk of the car, which had been parked in the lot of an apartment complex in the Alexandria section of Fairfax County.

Virginia State Police opened the trunk and recovered more than a kilogram of cocaine, with a street value of between $250,000 and $1 million, depending on how heavily the drug is diluted, they said.

The driver and a male passenger, both believed by police to be from Maryland, disappeared into the high-rise apartment complex at 4949 Manitoba Dr., where they abandoned the car.

Police would not release the name of the driver who was issued the speeding ticket.

"This is a pretty significant amount of cocaine," said Officer T.T. Clarke, a narcotics agent with the state police bureau of criminal investigation.

"It is a problem that seems to get worse every year. The more men and time we put into it, the more drugs there seem to be out on the street. And when you see those Florida plates, of course it arouses suspicion in some cases."

The occupants of the rented car apparently were aware that state troopers were following them when they abandoned the vehicle, police said. At that point the police summoned the drug-sniffing dogs, whose reaction prompted the search.

Police cannot search a car without permission or reason to believe that a crime has been or is about to be committed, but it is legal for them to follow a vehicle. Officer King asked the driver if he was in possession of drugs, and he said that he was not.