Fire investigators have confirmed arcing power lines caused the wind-blown blaze that destroyed dozens of homes on the southwest side of Reno in November.

A report issued by the Reno Fire Department on Friday says an electrical engineer from the U.S. Bureau of Alcohol, Tobacco and Firearms concurred in its findings. The fire destroyed 26 homes and damaged 17.

Fire Chief Michael Hernandez said earlier he suspected power lines sparked the Nov. 18 fire but he stopped short of ruling that the formal cause. The report says a tree branch probably was blown into lines.

The 1,935-acre fire was quickly spread by gusts of up to 85 mph.

Another 29 homes burned south of Reno last week in a fire started accidentally by a man discarding fireplace ashes.