An estimated 77 homes have been damaged—and 17 totally destroyed—by the wind-driven Saddleridge Fire, according to new estimates released this week by fire officials.

There has been no cause attributed to the wildfire, which sent tens of thousands of residents fleeing from their homes and charred 8,391 acres in the northern San Fernando Valley. But arson investigators have determined that it ignited at a 50-foot by 70-foot area beneath a high voltage transmission tower in Sylmar.

“We are aware of a story out there in the media from a witness who saw fire falling from a transmission tower,” Los Angeles Fire Chief Ralph Terrazas said last week. “We believe that witness, and someone else who said something similar.”

On Friday, Southern California Edison alerted the California Public Utilities Commission that its electrical equipment may be linked to the wildfire, the San Francisco Chronicle reports.

According to the Chronicle, which reviewed radio transmissions, the first firefighters to spot the flames reported to dispatchers it was “a quarter-acre under the power lines.”

”Out of an abundance of caution we notified the CPUC on Friday, Oct. 11 that our system was impacted near the reported time of the fire,” spokesperson Susan Cox told City News Service.

In a statement, the Los Angeles Fire Department said investigators from Edison and private insurance companies were at the ignition site. It said its investigators “continue to work around the clock in steep terrain” to determine a cause.

The fire broke out around 9 p.m. Thursday near the 210 Freeway at Yarnell Street in Sylmar, amid 50 mph wind gusts and humidity as low as 3 percent.

The flames swept west and south after jumping the 5 Freeway, spreading into the “northernmost reaches” of Porter Ranch. One man died Friday of cardiac arrest while trying to protect his home with a garden hose in Porter Ranch.

It burned at a rate of 800 acres per hour, blackening hillsides and indiscriminately gutting homes, and TV news reporters on scene described the firefight as a game of “whack-a-mole.”

“You can imagine the embers thrown in the wind have been traveling a significant distance,” Terrazas said. “Embers at this fire have traveled downwind over one mile.”

For two days, an estimated 1,000 firefighters, aided by helicopters and a super scooper, battled gusty winds and bone-dry conditions, and an estimated 100,000 residents remained under mandatory evacuations, even where there were no active flames. All evacuation orders were lifted Sunday.

“I saw burns that came up to the backyards of hundreds, if not thousands of homes,” Terrazas said. “That took a lot of effort, and to not have any serious firefighter injuries is amazing.”

As Santa Ana winds eased Saturday afternoon and weather conditions grew more favorable, firefighters built containment lines around the blaze. As of Tuesday morning, containment stands at 45 percent.