UPDATE - The two people killed in a crash Monday evening were two girls, 12 and 6 years old.
Big Horn County Coroner Terry Bullis said the girls were from the Busby and Lame Deer area.
They died after the vehicle they were in, a 2006 GMC Yukon, driven by a 15-year-old boy, drifted out of the eastbound lane on U.S. Highway 212.
A report by the Montana Highway Patrol states the vehicle rolled when it hit a culvert, ejecting three of the six passengers.
The report also states alcohol may have been a factor in the crash.
The other passengers were a 13-year-old girl, a 5-year-old boy and a 15-year-old girl.
The MHP report states no one was wearing a seat belt and everyone was taken to the emergency room in Lame Deer. Their current conditions are unknown.
A 2001 Dodge Stratus driving through the scene struck one of the ejected passengers.
The driver and two passengers of the Stratus, all females in their early 20's, were also taken to the Lame Deer emergency room. Their conditions are also unknown.
Terry Bullis said the names of the girls killed in the crash will likely be available Tuesday afternoon.
A fatal crash in Big Horn County claimed two lives Monday night.
Montana Highway Patrol Trooper Justin Moran said an SUV carrying six people drifted off the road on U.S. Highway 212 between Busby and Lame Deer around 11 p.m. Monday.
The driver lost control, struck a culvert and rolled.
Three people were ejected and two of them have died from their injuries.
Shortly after the crash occurred, a second vehicle driving through the crash site ran over one of the ejected passengers.
The Montana Highway Patrol and Bureau of Indian Affairs are working together to determine which incident lead to the fatality.
The other passengers involved in the crash were also taken to the hospital for medical attention. The extent of their injuries are unknown.
Moran believes lack of seat belt use was a factor, but there were no signs of speeding or alcohol use.