As firefighters worked to contain wildfires across California Saturday, residents began returning to their homes, business owners surveyed the damage and officials shifted their attention to what had gone wrong and what could be done to prevent — or at least temper – what has become a near-constant threat.

The state was not in the clear yet: The Maria Fire was still burning in Ventura County, and red-flag warnings were still in effect until Saturday evening. But firefighters had contained 20 percent of the 9,400-acre fire by the afternoon, and many residents were allowed back to their houses.

For power companies, the heat only continues to build. Southern California Edison, one of the state’s largest electric companies, disclosed on Friday that just 13 minutes before the Maria Fire began, it had begun to return electricity to a nearby circuit after a power shut-off intended to prevent wildfires.

Ron Gales, a spokesman for the company, said that it was unclear whether the return of electricity was related to the fire but that the company had alerted a state regulator and would cooperate with any investigative agencies.

Politicians and residents have increasingly expressed outrage at power companies for sparking some of the state’s deadliest wildfires. That anger grew in recent weeks when the companies turned off power to millions of people to prevent starting more.

Southern California Edison’s chief executive, Pedro J. Pizarro, told investors on a telephone conference this past week that a preliminary investigation from the Ventura County Fire Department found that the company had most likely been responsible for the Woolsey Fire last year. The blaze killed three people and destroyed more than 1,600 homes and businesses.

“Absent additional evidence, SCE believes it is likely that its equipment was associated with the ignition of the Woolsey Fire,” Pizarro said on the call.

During several public safety shut-offs in October, Southern California Edison cut off electricity to more than 200,000 customers and Pacific Gas and Electric’s shut-offs put nearly a million customers in the dark, mostly in Northern California.

Despite those blackouts, the companies and fire investigators are reviewing whether the utilities’ equipment was responsible for a number of recent fires. PG&E said there appeared to be a “broken jumper” on a 43-year-old transmission tower near the start of the Kincade Fire, the largest wildfire in the state this year.

Gov. Gavin Newsom of California said Friday that he was appointing an “energy czar” to guide PG&E out of bankruptcy and that if those efforts were not successful, the state would consider a public takeover of the company, a move that some state and federal lawmakers have supported.

Ken Wilson was trying to focus Saturday afternoon on what remained after the Kincade fire in Sonoma County last week leveled almost all of the Soda Rock Winery, which he has owned since 2000. He lay planks of wood over barrels to create a makeshift tasting room in the property’s barn, the lone building still standing, and invited people to come and swirl some glasses.

Wilson said it was difficult to even grasp the combination of long-term and immediate factors that led to a large blaze like the Kincade Fire, which has burned 77,750 acres and was 72 percent contained Saturday.

“As much as you’re frustrated with PG&E a little bit, you’re frustrated with a lot of things,” he said. “I’m sure there will be changes, but I’ll try to let the lawmakers sort that one out. It’s going to be a mess for a long time.”