A routine traffic stop yesterday on Interstate 95 in Delaware County led to a high-speed pursuit when the driver stepped on the gas and a state trooper pumped a bullet into the passenger's thigh, police said.

The driver, Robert Hills, 23, of Virginia, was being questioned last night and was expected to be charged with aggravated assault of a police officer, said Trooper Jonathan Sunderlin, a state police spokesman.

The passenger in the rental car - a black Kia with Maryland plates - was being treated for the gunshot wound at Crozer-Chester Medical Center and likely faces the same charges.

Shortly after 3 p.m. yesterday, Trooper Joseph Thompson stopped the car on southbound I-95 near the Route 420 exit, and a backup police officer from Tinicum Township arrived, Sunderlin said.

While the backup officer - whom Sunderlin did not identify last night - was speaking with the driver, Thompson noticed that the passenger, who was still inside the car, had a gun.

"Trooper Thompson drew his gun," Sunderlin said, and the driver "was able to force his way back inside the Kia."

"The driver put the vehicle in drive and attempted to drive away," he said. "The Tinicum Township officer and the trooper were still partially inside the vehicle. They were dragged slightly down the highway."

According to state police, Thompson was hanging on the car and fired the shot, then was thrown from the car as it sped off. Cops from surrounding departments descended on the area. The men were arrested at the hospital, where they had gone on their own.

Last night, investigators were waiting for a judge to sign a warrant to search the car. It was unclear if the passenger had fired a gun, Sunderlin said, but neither the state trooper nor the Tinicum cop was seriously hurt.