Fast-moving wildfires forced evacuation orders for more than 100,000 people and seriously injured two firefighters in Southern California on Monday as powerful winds across the state prompted power to be cut to hundreds of thousands to prevent utility equipment from sparking new blazes.

A smoky fire exploded in size to more than 11 square miles after breaking out around dawn in Orange County, south of Los Angeles.

Gusts pushed flames along brushy ridges in Silverado Canyon and near houses in the sprawling city of Irvine, home to about 280,000 residents. There was no containment.

Two firefighters, one 26 and the other 31 years old, were critically injured while battling the blaze, according to the county’s Fire Authority, which did not provide details on how the injuries occurred. They each suffered second- and third-degree burns over large portions of their bodies and were intubated at a hospital, officials said.

California Wildfires
Firefighter Raymond Vasquez battles the Silverado Fire in Irvine (Jae C Hong/AP)

Nearby, a much smaller fire in the Yorba Linda area prompted the evacuation of at least 10,000 people, officials said.

Helicopters dropping water and fire retardant were grounded for much of the afternoon because strong winds made it unsafe to fly. However, a large air tanker and other aircraft began making drops again several hours before sunset.

Officials did not immediately know the cause of the fires.

California Wildfires
A helicopter drops retardant on the Silverado wildfire (Mindy Schauer/The Orange County Register/AP)

Electricity provider, Southern California Edison, shut off power to nearly 40,000 customers in six counties — which includes the wildfire areas — as a precaution against the gusts knocking down equipment or tossing tree branches into power lines and sparking blazes.

In the northern part of the state, Pacific Gas & Electric began restoring power to some of the 350,000 customers — an estimated one million people — in 34 counties that were left in the dark on Sunday amid some of the fiercest winds of the fire season.

PG&E said it had restored power to nearly 100,000 customers as winds eased in some areas, with electricity to be back on at the other homes and buildings by Tuesday night after crews make air and ground inspections to make repairs and ensure it’s safe.

California Wildfires
A huge plume of smoke generated by the Silverado Fire rises behind homes in Irvine (Jae C Hong/AP)

A dozen reports of damage had been received, PG&E said.

However, the fire threat was far from over in many parts of PG&E’s vast service area.

“We’re already starting to see winds pick back up,” said Scott Strenfel, PG&E’s head of meteorology, saying winds had hit 50mph.

The winds were expected to calm on Monday night before renewing again on Tuesday, the National Weather Service warned.