Authorities across Southern California were beefing up patrols Saturday night, hoping to catch the person or persons responsible for more than 35 fires over the last two days.

Los Angeles police and fire officials were trying to determine whether the fires were the work of one arsonist or several. Some officials believe it would be difficult for one person to have set all the fires but have definitely ruled out a lone arsonist, law enforcement sources told The Times.

On Friday morning, 21 fires were started in a relatively small area around Hollywood and West Hollywood. On Friday night and Saturday morning, 16 more fires were reported. They were similar to the ones in Hollywood but were spread out over a much larger area.