Los Angeles County Sheriff Robert Luna said detectives are continuing to investigate the possible causes.
"Everything is absolutely on the table," he said.
Lightning - the most common source of fires in the US - has been ruled out as a cause for the Palisades and Eaton fires.
Nor has there been any official indication so far that arson or utility lines - the next two biggest culprits in sparking fires - caused any of the conflagrations.
California's very wet years of 2022-23 brought about a huge growth of vegetation, which dried out in the drought of last year, creating abundant kindling.
A combination of an exceptionally dry period - downtown Los Angeles has only received 0.16 inches (0.4cm) of rain since October - and powerful offshore gusts known as the Santa Ana winds have also created ripe conditions for wildfires.
BBC weather forecaster Sarah Keith-Lucas says there is no rain forecast in the area for at least the next week.
Although winds were expected to ease slightly later Friday into Saturday, forecasters warned that they would pick up again on Sunday into Monday.