Fire crews are gaining ground against a Northern California wildfire that forced more than 1,000 people to flee and destroyed 12 homes.

California’s department of forestry and fire protection said the fire in Lake County north of San Francisco is 25% contained, up from 17% on Tuesday.

The blaze burning through dry brush, grass and timber has scorched 21 square miles since it started on Saturday, and is threatening 600 buildings.

Firefighters tackle the blaze
Around 1,500 people have been evacuated (AP)

State fire officials say high temperatures, low humidity and erratic winds helped the blaze expand on Tuesday, and warned of the same weather on Wednesday.

At least 1,500 people remain under mandatory evacuation.