BILLINGS, Mont. (AP) — Wyoming’s Northern Arapaho Tribe has sued the leaders of the Eastern Shoshone Tribe, escalating a long-running political dispute between two American Indian tribes that share a reservation.

The lawsuit was filed Monday in U.S. District Court in Montana. It claims Eastern Shoshone leaders improperly approved mineral leases and made hiring decisions without consulting the Northern Arapaho.

Also named as defendants were representatives of the U.S. Bureau of Indian Affairs.

The Wind River Reservation near Lander is home to about 4,000 Eastern Shoshone and 8,600 Northern Arapaho.

The suit comes after the Northern Arapaho two years ago dissolved a joint government with the Eastern Shoshone, saying it created barriers to economic development and often wasted time.

Representatives of the Eastern Shoshone and the BIA could not be reached immediately for comment.