Randallstown - Gunfire erupted at a Baltimore County high school, injuring four male students who were leaving a charity basketball game, a police official said.

Three of the students had injuries that were not life-threatening, while the fourth was in surgery, said Baltimore county police chief Terrence B Sheridan.

One student was released from the hospital on Friday night.

The motivation for the attack was not immediately known, but Baltimore county executive James T Smith jun told WBAL-TV that it was a "street crime that happened on school grounds".

Witnesses told police a car with about four people inside pulled up to Randallstown High School about 16:30, and the driver and a passenger got out of the car, said police spokesperson Bill Toohey.

Security camera wasn't working

The driver shot four or five times, then handed the gun to the passenger, who also fired. The car - a black BMW with tinted windows - then sped off.

An officer looking for the car was told by witnesses that three people had fled from a black BMW, Sheridan said. The officer captured a suspect.

The shooting occurred after the basketball game, attended by about 300 students.

A security camera was pointed at the area of the shooting, but it was not working, Toohey said.

Anxious parents waited outside the school, blocked from entering by police tape.

A woman who answered the telephone at the school's main office said school officials could not comment because "clearly, they are trying to contact families".

Randallstown High School has about 1 700 students and is in northwest Baltimore county, about 16km from Baltimore.

Edited by Iaine Harper