Authorities say a nine vehicle pileup on a suburban St. Louis highway has left two people dead and six others critically injured.

West County EMS and Fire Protection District spokeswoman Kim Bacon says the collision occurred at about 3:30 p.m. on Tuesday on U.S. 40 in west St. Louis County.

She says a dozen people were injured and that six transported from the scene were hospitalized in critical condition.

Bacon says a tractor trailer was involved in the collision.

Authorities have not determined what caused the pileup.