A fire has broken out at the border of Los Angeles and Ventura counties and is spreading rapidly, threatening numerous hillside homes in the Calabasas and Hidden Hills areas.

UPDATE Jan. 9, 8:35 p.m. The Kenneth Fire that erupted Thursday afternoon on the border between Los Angeles and Ventura counties is reportedly being investigated as an arson case, with one person in custody. As of Thursday evening, the blaze has expanded to 960 acres, with no containment.

A mandatory evacuation order was issued for the area near Calabasas Officials expected the blaze to continue growing.

Firefighters are racing to contain a new wildfire that broke out close to homes in the area of Calabasas and Hidden Hills, northwest of Los Angeles, on Thursday afternoon.