SLIPPERY ROCK, Pa. -- A tractor-trailer and car collided along Route 8 in Slippery Rock Township around 1:45 p.m. Monday.

Witnesses told police there were several explosions after the impact of the crash. The car ended up under the tractor-trailer.

Channel 11 News has learned four people have died. A family of five was in the car.

STAT Medivac crews told Channel 11 that one person has been flown to Mercy Hospital's burn unit with what appears to be third-degree burns on 95 percent the person's body.

The tractor-trailer driver suffered minor injuries. There is no word on their conditions.

State police are at the scene along with hazmat crews.

Officials said emergency workers are being instructed to wear masks because they don't know what type of substance was inside the big rig.

Police said Route 8 will be closed while crews clear the scene and investigate the accident.

View Images Of Route 8 Accident