California authorities arrested a suspected drug courier yesterday who had been sought throughout the nation after he allegedly raided an Anne Arundel County foster home last month to abduct the infant son he had left on an airplane.

William Thomas Forrer, 32, of Virginia, was arrested at 4:15 p.m. Pacific time by police in Salinas, Calif., after a car and foot chase in which a police car was rammed, shots were fired and the van the suspect was allegedly driving crashed into a building, the FBI reported last night.

Forrer's son Zachary, 10 months old, "was in the van and was tossed around slightly as a result of the chase and the crash," a spokesman for the Baltimore FBI office said.

The baby was treated for bumps and bruises at a Salinas area hospital and released, according to the FBI. It said he was then taken to the Monterey, Calif., Department of Social Services for eventual return to the Anne Arundel County social services department.

Forrer was sought for escape from prison before the April 21 abduction. The FBI said last night that he would be held over the weekend in the Salinas jail pending an appearance Monday before a federal magistrate.

Salinas police said they spotted a rented van yesterday and pursued it for eight miles. Detective Andy Enni said the van's driver attempted to run down an officer on a motorcycle. The officer "fired three rounds." Enni said the shots were enough to "make the driver sort of lose control." The detective said the van rammed a patrol car and while the van continued to move, its driver jumped out. The van smashed into the side of a bank.

Salinas police said Forrer, who was injured slightly, was arrested after a chase of several blocks.

According to Anne Arundel County police, Forrer, with the help of other persons, had overpowered a county social worker and forced her to lead them to the home of the family caring for Zachary. Forrer allegedly persuaded the family to surrender the child by posing as an FBI agent, according to the police account released last month.

Forrer's son had been a ward of the state since Feb. 21, when, police allege, he was left on an airplane seat at Baltimore-Washington International Airport. Police alleged that Forrer fled from a jetliner after he realized he was under surveillance. They alleged that he left marijuana on the plane, and pursued by state troopers, ran through the terminal and escaped.