Two brush fires in Southern California on Wednesday prompted evacuations and orders to shelter in place and left tens of thousands of people without power as firefighters battled dangerous weather conditions that could further fuel the blazes.

In Ventura County, the Mountain Fire, which started on Wednesday, had burned up to 1,000 acres and injured several people who were taken to hospitals, the Ventura County Fire Department said. Their conditions were not immediately clear.

The Mountain Fire, which had not been contained, was threatening numerous structures, according to fire officials. The Ventura County Fire Department said 140 firefighters, aided by helicopters and other aircraft, were working to contain it while dealing with strong winds that were worsening conditions. The California Department of Forestry and Fire Protection, known as Cal Fire, said evacuation orders were in effect for parts of Ventura County. It was not immediately clear how many residents were under orders to evacuate.

Farther south, along the Pacific Coast Highway in Malibu, the Broad Fire began early on Wednesday, burning about five to eight acres before quickly growing to 50 acres, officials in Malibu said. The fire had not yet been contained and had affected at least two structures, according to California fire officials. Residents near the fire in Malibu were under shelter-in-place orders, but officials said that evacuation orders were possible.

Pacific Gas & Electric announced a power shut-off on Wednesday to prevent further wildfires. More than 16,000 customers across Los Angeles and Ventura Counties were without power on Wednesday, according to poweroutage.us, which tracks data from utility companies.

The fires were burning as meteorologists warned that weather conditions, which were dry and windy on Wednesday, were ripe for fires to spread rapidly. Los Angeles and Ventura counties were under a red flag warning through Friday, and the National Weather Service warned residents of a “particularly dangerous situation.”

Parts of Southern California could see damaging wind gusts of up to 80 miles per hour, which could down trees and cause power outages in addition to spreading the flames, the Weather Service said. Parts of Ventura County were also under a dense smoke advisory, meaning that smoke in the area could make driving conditions dangerous.

This is a developing story.