Eleven cars slammed into each other in a chain reaction on the Saw Mill River Parkway near Irvington Friday apparently because of a construction truck.

Police had to shut down the northbound side of the parkway, causing traffic to back up in the middle of rush hour. Police believe a truck making a delivery to a construction site was what set off the accident. Three people were taken to the hospital and seven cars had to be towed off the parkway.

Trucks are normally prohibited from using the Saw Mill River Parkway. Police are investigating whether the driver of the truck had clearance to be on the parkway.