RAPID CITY, S.D. (KELO) — A mechanical failure is to blame for starting the Auburn Fire in the Black Hills on Monday.

Wildland officials say it started with earth moving equipment that was sitting in a field on private property and not used for a while.

It quickly spread, reaching nearly a thousand acres and forcing some people to temporarily evacuate their homes. At last report, the fire is at least 50-percent contained.

Officials say residents should still expect to see smoke coming from fuel burning within the fire perimeter.