LOS ANGELES (AP) — Dry vegetation fueled three wildfires near Los Angeles amid warnings Friday that the risk of new blazes erupting was high as temperatures spike and humidity levels drop during a statewide heat wave.

A huge forest fire that prompted evacuations north of Los Angeles was just 12% contained and after threatening more than 5,400 homes, it had charred 17 square miles (44.5 square kilometers) of brush and trees.

Cooler overnight temperatures helped firefighters increase containment of that fire, but the forecast called for hot, dry weather with extremely dangerous fire conditions because of possible gusty winds, a fire update said Thursday night.

California's heat wave was expected to last through the weekend, bringing triple-digit temperatures and extreme fire danger to many parts of the state.

Preliminary damage assessments found that at least three structures burned in the Lake Hughes area north of Los Angeles, but authorities said they believed more had been damaged or destroyed.

There was no containment of a blaze that blackened foothills above the Los Angeles suburb of Azusa. It churned through nearly 4 square miles (10 square kilometers) of brush and was moving away from homes, but some evacuations were ordered.

Another blaze came dangerously close to a neighborhood in the city of Corona, east of Los Angeles, before crews controlled it. And a Northern California fire in the community of Sloughhouse, near Sacramento, burned about 500 acres (202 hectares) before firefighters stopped its forward spread.