Although the cause of the fire remains uncertain, it may have been started by a hunter's campfire[3] or an exploding tank of butane gas.

Fifty men on a crew led by Supervisor Nash-Boulden were trapped, but they managed to survive after lighting a backfire on the canyon slope, pulling in fresh air and opening an escape route.

High temperatures, low humidity and 50 miles per hour (80 km/h) winds sent the fire burning quickly through the thick chaparral covering the mountains.

By midday on September 8, the fire had grown to 28,000 acres (11,000 ha) and was rapidly spreading to the south and east.

By September 13, the fire had burned as far north as Reyes Peak (near Pine Mountain), and the lookout tower there was destroyed.

[6] By September 18, it had reached Santa Paula Peak, more than 30 miles (48 km) east of Matilija Creek.

A heavy fog came in from the Pacific Ocean, elevating humidity, and by September 20, crews had managed to cut a line around the entire fire and contain it.

"[6] U.S. Forest Service officials cited inadequate fire lookout coverage as the primary reason for the failure to control the blaze.

The fire started in a place difficult to see from existing lookouts, and may have burned for hours before the smoke was initially spotted.

[9] Large debris flows occurred in the rainy seasons after the fire,[10] causing extensive property damage and silting in reservoirs.