Hattiesburg Police Department spokesman Ryan Moore told news outlets the wreck happened late Saturday afternoon at an intersection in the town.
A Forrest County sheriff’s deputy was taken to a hospital with injuries that appeared to be minor.
The county coroner has not yet released the names of the dead people who were in the other vehicle.
Sheriff’s Investigators Phillip Hendricks said the deputy was on duty but was not involved in a chase or emergency when the two vehicles collided.
The Mississippi Highway Patrol is helping in the investigation.