Cause for Twisp fire released

SEATTLE  — An investigation by the Washington state Department of Natural Resources found that tree branches rubbing on a power line started the 2015 blaze near Twisp that killed three firefighters.

The Seattle Times reports ( ) the DNR document was obtained through a public records request. The report says ignition likely happened as a light wind moved the branches and a sagging Okanogan County Electrical Cooperative distribution line on Aug. 19.

The investigation says burning foliage then dropped to the ground and spread flames.

A utility official told investigators the power lines are maintained to standards, with trees removed every three years or whenever deemed necessary. In the area where the fire began, the lines were last cleared during the 2012-13 winter.

The report didn't comment on the question of potential negligence.