EL SEGUNDO, Calif. (CNS) — More than a dozen people were injured Monday, three of them critically, in a crash involving a City of Los Angeles commuter bus and a parked big rig in El Segundo.

The crash occurred at around 8:25 a.m. in the 5600 block of West Imperial Highway, according to the Los Angeles Fire Department, which was assisting El Segundo police and fire personnel. The Los Angeles Commuter Express bus wound up on its side.

Also assisting at the scene were personnel from the Manhattan Beach and Redondo Beach Fire Departments, El Segundo Fire Chief Deena Lee told City News Service.

Lee said the bus was eastbound on Imperial Highway when it hit the driver of a parked big rig, who was offloading a scissor lift from the vehicle, and the bus overturned and ended up on the driver's side.

The truck driver and two people from the bus were transported for hospital treatment in critical condition, Lee said.

Four other people on the bus were also transported for hospital treatment, two of them with moderate injuries and two with minor injuries, according to Lee. Thirteen other people aboard the bus were examined at the scene and were treated and released, according to Lee.

Imperial Highway was closed in the area while an investigation was conducted into the circumstances of the crash, according to the California Highway Patrol.