A U.S. Postal Service truck apparently broadsided a car carrying five people in downtown Minneapolis Sunday night, injuring four of them seriously, police said.

The accident happened about 9 p.m. at the intersection of 5th Avenue S. and S. 4th Street, police Sgt. William Palmer said.

The truck driver, who was the only occupant of the truck, received minor injuries; all six people involved in the accident were taken to Hennepin County Medical Center, Palmer said.

Their conditions were unavailable late Sunday.

The cause of the accident remains under investigation.