VALHALLA - A Westchester County police officer was seriously hurt when he was struck by a passing car as he helped a disabled vehicle on the side of the highway Saturday night.

The incident happened on the Hutchinson River Parkway under the Mamaroneck Road underpass shortly after 9:30 p.m.

Witnesses say the officer had parked his cruiser so that it blocked the right lane for a tow truck, with the cruiser's lights flashing. He was walking to the disabled car with his flashlight in hand when he was struck.

The officer, who has not been identified, is listed in serious but stable condition at Westchester Medical Center in Valhalla.

Traffic was shut down for hours as police questioned the driver.

The driver was a 63-year-old woman from Massachusetts. Police say she tested negative for drugs and alcohol, and no charges have been filed at this time.