On Sept. 7, Portland General Electric turned off the power grid near Mount Hood, leaving thousands without electricity but reducing the potential that a windstorm would blow down sizzling live power lines into dry brush.

Seventy miles south, along the Santiam Canyon, several power companies didn't turn off their grids. A Sept. 10 incident report by the Northwest Interagency Incident Management Teams, which coordinate regional fire response, shows the result: "At least 13 new fires were started between Detroit and Mehama from downed power lines during the peak of Monday's wind event."

Those new fires fed into the Beachie Creek Fire, the Cascade Mountain blaze that has threatened some of Oregon's most beloved natural areas, including Silver Falls State Park and Opal Creek.

It's not clear which companies' lines caused the fire, but fire incident officials say both PGE and PacifiCorp operate in the area.

"We are aware of reports that fires have been started by electrical equipment," says PacifiCorp spokesman Drew Hanson. "We have no information at this time to know if any of the referenced fires were in our service area."

PGE says it has only a transmission line in the Beachie Creek region that the company believes was deenergized by smoke from the fire. "PGE is not aware of any wildfires caused by our equipment," says PGE spokesman Steven Corson.

State officials will spend months examining what factors contributed to Oregon's catastrophic fires. The incident reports, which WW reviewed this week, provide a few initial clues.

Almeda Fire: Killed three and destroyed 1,500 homes in Phoenix and Talent.

Cause of the fire: A suspected arson on Sept. 8 is under investigation. (No arrests have been made for the initial cause of the fire, but one person was arrested on suspicion of setting a second fire that joined the Almeda blaze.) The Douglas County sheriff has repeatedly said anti-fascist extremists are not suspects, despite widespread internet falsehoods.

Beachie Creek Fire: Killed 4 people and ripped through Detroit and Mehama on Sept. 8, catching people there by surprise.

Cause of the fire: Originally, lightning on Aug. 16, but according to a Sept. 10 incident report, power lines started more, and "then on Tuesday a large front of wind-driven fire ran through the city of Detroit from the east."

Lionshead Fire: Started on the Confederated Tribes of Warm Springs Reservation, reached west and combined with the Beachie Creek Fire.

Cause of the fire: Lightning Aug. 16.

Riverside Fire: The blaze closest to Portland, it threatened Estacada and Molalla in Clackamas County.

Cause of the fire: Incident reports say it was human caused but provide no further details.