BILLINGS, Mont. (AP) – Authorities say the Ash Creek fire near southeastern Montana's Northern Cheyenne Indian Reservation has burned 18 homes and grown to 100,000 acres.

Fire officials in a Wednesday briefing in Billings said there are 319 structures within the 156-square-mile perimeter and the fire is uncontained.

The fire began Tuesday 10 miles east of Lame Deer on and has led to the evacuation of an unknown number of residents in Ashland and St. Labre. More than 100 firefighters are responding to the fire now burning on state and private land off the reservation.

U.S. Forest Service spokeswoman Paula Short says the tribe is managing the response, but a Department of Natural Resources and Conservation team is expected to take over management of the fire on Wednesday.