A truck struck a horse and buggy in central Pennsylvania, killing a woman and an 8-year-old boy and seriously injuring four other people, authorities said.

State police in Clinton County say the eastbound UPS box truck drifted into the path of the horse and buggy "for unknown reasons" and struck the left horse shaft, the rail that goes alongside the horse, "impaling" the vehicle and causing it to overturn at about 6:45 p.m. Friday in Logan Township.

Police said 36-year-old Rachel Beiler, 36, of Loganton and the child were pronounced dead at the scene by the county coroner. The boy's name was not released.

State police say a 37-year-old man was taken to Geisinger Medical Center in critical condition. They said a 13-year-old boy and two girls aged 11 and 14 also had major injuries.

Authorities said the truck traveled 100 feet after the collision and hit a walnut tree. The 55-year-old woman who was driving was reported to have a minor injury.

Police said the horse was also killed, and it and the buggy were removed by the Amish community. The cause of the crash is under investigation and no charges were immediately filed.