UPDATE: Fire investigators say the blaze started by a combination of high temperatures caused WWII-era smokeless gun powder to spontaneously combust. The nearly 75-year-old powder was breaking down and the owner was planning to discard it, but hadn't yet done so.

The powder ignited and spread to nearby combustibles before spreading to the attic through the eave. Neighbors report hearing a large boom prior to the blaze. Investigators believe the explosion was the result of a can of WD40 catching fire.

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BEND, OR -- The Bend Fire Department is investigating the cause of a house fire on Northwest Davenport, Monday night. Crews responded just after 8:30 p.m., and found smoke coming from the roof and fire on the back side of the home.