Groton ― A state police sergeant suffered a fractured left arm Thursday afternoon when his cruiser was struck from behind by a car driven by a New London man, police said.

The 3:05 p.m. crash shut down the northbound lanes of Interstate 95 just north of the Gold Star Memorial Bridge for more than four hours. Traffic was being diverted off the highway at Exit 85 and allowed to reenter the highway at the next on ramp in Groton.

According to a state police report, Sgt. Christopher Vaillancourt, 43, had stopped his cruiser to pick up a piece of construction equipment on the highway. That’s when a car driven by Bill Ray Goff, 25, of 310 Bayonet St., which was traveling in the right lane of three, braked but struck the cruiser from behind. The report states the cruiser’s emergency lights were flashing at the time of the crash.

After impact, Goff’s car began to spin and struck a car and an SUV. Vaillancourt and Goff, who reported head pain and sustained a lacerated finger and hand, were taken to Lawrence + Memorial Hospital for treatment. No one was injured in the other car and SUV.

State police are investigating the crash. Witnesses or anyone with information are asked to contact State Police Troop E in Montville at 860-848-6500.

During the late afternoon traffic was backed up on Interstate 95 in Waterford and south on Route 32 to the Interstate 395 intersection. Early Thursday evening, traffic was backed up into downtown New London. Traffic began flowing normally over the bridge after 8:15 p.m.