Names of the six people involved are not being released pending notification of family members, the Highway Patrol said in a news release.
Two children in the Buick, a 4-year-old female and a 2-year-old male, died at the scene. Both were wearing seatbelts, the Highway Patrol said.
The two other occupants in the Buick, both females, suffered life-threatening injuries. The 28-year-old driver, who was not wearing a seatbelt, was ejected from the vehicle. She was taken to an Aberdeen hospital and later airlifted to a Fargo, N.D., hospital. A 7-year-old female passenger, who was wearing a seatbelt, was taken to an Aberdeen hospital.