The Skirball Fire that destroyed six structures and burned 422 acres in the hills of Bel-Air broke out because of an illegal cooking flame ignited at an area homeless encampment, officials said Tuesday.

The fire was 85 percent contained at its last assessment Tuesday after being sparked in the early morning hours of last Wednesday, Dec. 6, in a bush area near where Sepulveda Boulevard crosses under the 405 Freeway, according to the Los Angeles Fire Department.

No one has been arrested in connection with the incident, and no one was present when LAFD visited the area of origin, officials said.

In addition to the six buildings razed, another 12 were damaged. It was unclear how many of the structures were homes.

The fire had forced hundreds of evacuations and closed down the world-famous Getty Center museum, as well as several area schools, including UCLA.

An assistance center was open to those who were affected by the Skirball, Creek and Rye fires at the Lake View Terrace Recreation Center, located at 11075 Foothills Blvd. It will operate Tuesday through Friday from noon to 8 p.m. daily, as well as on Saturday from 8 a.m. to 4 p.m.

So far, three firefighters have been injured while combatting the blaze. Another 69 firefighters remained on the fire lines Tuesday working to achieve 100 percent containment.

LAFD did not say when they expect the fire to be fully contained.

The Skirball is the first of the six fires that broke out across Southern California last week to be assigned a cause. However, the National Park Service estimates that 90 percent of wildfires nationwide are caused by humans.