BILLINGS, Mont. (AP) — Tribal wildlife officials say a family of grizzly bears was killed as the female bruin and her two cubs tried to cross a highway on northwestern Montana's Flathead Indian Reservation.

The Confederated Salish and Kootenai Tribes wildlife program posted a photo of the animals and a statement saying the female bear had been used for years to collect data on grizzly movements on the reservation.

The deaths bring to four the number of grizzlies killed this year on a 13-mile (21-kilometer) stretch of Highway 93 near Ronan.

Tribal wildlife officials say bears increasingly are dispersing west across Montana's Mission Valley. They warn motorists to watch for the animals crossing the highway.

Vehicle collisions are a frequent killer of grizzlies, which are protected as a threatened species in the area.