Police are investigating a crash on Route 1 in Bucks County during a traffic stop that left a police officer and five others injured.

The three-vehicle car chain-reaction crash occurred about 11 p.m. Sunday after a police officer pulled over a car for speeding in Falls Township, officials said.

While the officer approached the stopped vehicle, a car with four people inside hit the police car, which then slammed into the stopped car, police said.

The driver of the striking car suffered serious head injuries and was taken to Helene Fuld Trauma Center in Trenton, police said.

The officer, the driver of the stopped car and the three passengers in the vehicle that hit the police car were taken to Aria Hospital Bucks County for treatment of what were described as non-life-threatening injuries, authorities said.

Police said speed and DUI appeared to be factors in the crash.

The investigation is continuing and no charges were immediately filed.