CAMARILLO, Calif. -

Firefighters building containment lines around a huge Southern California wildfire are now dealing with muddy and slippery conditions as rain moves in.

Ventura County Fire spokesman Tony McHale said Monday that the wet weather has significantly reduced fire activity but it's also caused crews to work more slowly and methodically. The blaze is 80 percent contained. Officials now expect full containment late Tuesday.

Investigators have ruled out arson as the cause of the fire that has charred 44 square miles at the western end of the Santa Monica Mountains.

At its peak, the fire threatened some 4,000 houses as it moved through neighborhoods of Camarillo Springs and Thousand Oaks. It damaged 15 homes.

East of Los Angeles, a fire that burned 510 acres in Riverside County is fully contained.