KULM, N.D. (AP) – The state fire marshal’s office says a Nov. 9 blaze that gutted the museum at the Whitestone Hill Battlefield State Historic Site in southeastern North Dakota was intentionally set.

Chief Deputy Fire Marshal John Elstad says investigators found that the museum door’s lock had been cut and artifacts were missing.

The State Historical Society says it plans to rebuild the stone-walled museum as soon as possible but that it might take a couple of years.

Whitestone Hill Battlefield is where U.S. Cavalry troops under Brig. Gen. Alfred Sully battled with Sioux warriors on Sept. 3, 1863. The Historical Society says it was the last major battle between soldiers and American Indians east of the Missouri River. Twenty-two soldiers and more than 100 Indians died.