Mandan Fire leaders say the Sunset Bluffs fire on Sunday appears to be the result of an accident.

They say they don't, however, know exactly how it started.

The Mandan Fire Department says they conducted an extensive investigation into the fire with the Mandan Police Department, including interviewing building occupants and witnesses, and examining physical evidence. They say they found no indications that the fire was intentionally set and ruled out natural causes such as lightning strikes.

The cause of the fire remains under investigation.