Updated at 3:45 p.m. Tuesday with information on cause of fire at Westgate QFC

A tree falling into a power line in Woodway caused Monday night’s outage to 1,500 Snohomish County PUD customers, and it’s been determined that a fire at the Westgate QFC around the same time was related to the grocery store’s generator, which kicked on when the power went out.

According to John Westfall, Fire Marshal for Snohomish County Fire District 1, the QFC fire, reported at 8:30 p.m. was caused by mechanical failure of an exhaust pipe from the store’s backup generator.

The generator is located on a platform above the QFC stockroom area in a refrigeration compressor room, Westfall said in an email. When a standoff clamp for the generator’s exhaust pipe fell out of place, the heated pipe made contact with combustible construction where it penetrated the roof. (A standoff clamp is meant to prevent a pipe from contacting a wall.)

The pipe’s exhaust passed through the ceiling and roof behind some mechanical equipment and piping in a place that was difficult to locate, and the smoldering fire was also not large enough to be obvious, he said. “When the heat and smoke vented from this area, it spilled into the ventilation intake and was distributed through the store,” Westfall explained.

The power outage, reported at 7:35 p.m., affected circuit 405, which serves not only Woodway but Edmonds’ Westgate and Point Edwards neighborhoods — plus a swath of downtown involving the Edmonds IGA store and Hamburger Harry’s restaurant. Circuit 405 has been an ongoing issue due to trees on wires, according to PUD.

Monday night’s incident began when a tree fell on lines at 22225 Woodway Park Road, the PUD said. Power was restored to 500 customers at 8:21 p.m. and remaining customers had power by 12:19 a.m. Tuesday.

Because of the size of the store, the incident was called in as a two-alarm fire. According to Fire District 1 spokesperson Leslie Hynes, one QFC employee was evaluated for smoke inhalation and treated at the scene.

My Edmonds News readers reported they spotted flashes of blue in the sky around the time of the fire, but PUD spokesman Bob Bolerjack said the PUD has received no reports of fuses or transformers blowing in the area.