The blaze, which started Tuesday, came six months after the Tea Fire destroyed about 200 homes in the Santa Barbara area.
The current fire has forced about 13,000 people to evacuate, said Derek Johnson, a spokesman for Santa Barbara County Fire Department.
Though there was no official count on homes destroyed early Thursday, one firefighter said he saw 20 homes scorched.
Eight firefighters were injured and the cause of the blaze has not been determined, emergency officials said.
"The fire is moving very, very rapidly," Santa Barbara County Fire Capt. David Sadecki said Wednesday. "This is an uncontrolled wildfire."