The Guiberson fire, which burned 17,500 acres in September 2009 was caused by a spontaneous combustion much pile. Santa Ana winds contributed to the fast-spreading fire which threatened 1,000 structures, with 600 homes being evacuated.

A total of 2,750 personnel were called out to battle the fire, including 200 fire engines, 32 bulldozers, 21 helicopters and 8 air tankers. A converted DC-10 jumbo jet, converted into an air tanker, was used to drop fire retardant on the flames.

The fire cost more than $9 million, and 10 firefighters were injured in the blaze, including smoke inhalation and heat-related injuries.

Mulch piles need to be turned regularly to prevent heat buildup and will combust if not properly maintained. The mulch pile owner has not been cited.