SANTA PAULA, Calif. — Ferocious winds in Southern California whipped up an explosive wildfire that forced thousands of homes to evacuate and could soon threaten a city of more than 100,000, authorities said.

The blaze broke out Monday and grew wildly to more than 15 square miles in the hours that followed, consuming vegetation that hasn’t burned in decades, Ventura County Fire Sgt. Eric Buschow said.

The winds were pushing it toward Santa Paula, a city of some 30,000 people about 60 miles northwest of Los Angeles. Most of the evacuated homes were in that city.

Authorities said that the city of Ventura, which is 12 miles southwest and has 106,000 residents, was likely to feel the effects soon.

“The fire growth is just absolutely exponential,” Ventura County Fire Chief Mark Lorenzen said. “All that firefighters can do when we have winds like this is get out ahead, evacuate people, and protect structures.”

Thomas Aquinas College, a school with about 350 students, has also been evacuated, with students going to their own homes or to those of faculty and staff, the college said in a statement.

One person was killed in an auto accident associated with the fire, officials said. They gave no further details.

At least two structures have burned so far, sheriff’s officials said.

Winds exceeding 40 mph and gusts over 60 mph have been reported in the area and are expected to continue, the National Weather Service said.

Firefighters and aircraft from neighbouring Los Angeles and Santa Barbara counties were pouring in to help, though the darkness and winds forced the grounding of planes late Monday night.

Thousands of homes were without power in the area.