Evacuated residents prepared to return to their burned-out streets as officials announced that an illegal campfire caused the inferno that destroyed more than 200 homes and charred 3,100 acres.

A U.S. Forest Service investigation found that the fire south of Lake Tahoe was built in a campfire-restricted area, but said there was no evidence it was deliberately set to spark the devastating wildfire that has displaced about 3,500 people.

• PHOTO ESSAY: Lake Tahoe Wildfire Jumps Fireline

Residents did not seem surprised by the news.

"Apparently kids hang out there," said Donna Barker, a 21-year resident of Tahoe Keys who evacuated on Tuesday, although her home was spared. "I don't think people think. It's a sad reality."

Because of tinder-dry conditions due to a lack of snow over the winter, the U.S. Forest Service had banned all campfires, charcoal grills, smoking and fireworks throughout the Tahoe basin.

The fire's cause was announced after a second straight day of mild winds that allowed firefighters to surround the blaze. The fire was 80 percent contained by Friday evening, U.S. Forest Service incident commander Rich Hawkins said.

"Firefighters came in this morning and felt even more comfortable about the approaching containment of this fire," he said. "I'm feeling pretty good about it."

However, officials cautioned it was too early to declare victory, with forecasters predicting winds could pick up again and hotspots still smoldering in some areas.

"Don't be complacent. There are still hazards out there," Kit Bailey, a U.S. Forest Service chief, told hundreds of firefighters Friday morning. "It's going to be a long, brutal summer."

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On Friday, residents were given limited access to some areas where all the destroyed homes are located — welcome news to residents who had waited all week to see the devastation for themselves.

Keith Cooney saw his rented home of three years engulfed in flames on a local news broadcast Sunday and came back to find only a bent metal garage door standing. He spotted a concrete swan given to him by a former neighbor in New Orleans, but not the fireproof box with his important papers.

"I gotta dig through this. This is going to be unbelievable," he said.

Elsewhere on Friday, a 3,500-acre wildfire near a gateway to Yellowstone National Park was 20 percent contained, firefighters said.

"We got a lot of work done today, but we're not totally done," said Jess Secrest, who supervises an incident team in charge of fighting the fire.

Evacuation orders remained in effect for 45 to 50 summer homes, a resort, several campgrounds and a ranger station.

Fire officials said the blaze was human-caused but released no other details about its source.

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