LOS ANGELES — A fast-moving wildfire forced evacuation orders for 70,000 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.

The smoky fire exploded in size to over 6 square miles (16 square kilometers) within a few hours of breaking out around dawn in Orange County, south of Los Angeles. Strong 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 didn’t 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.

Kelsey Brewer and her three roommates decided to leave their townhouse before the evacuation order came in. The question was where to go in the pandemic. They decided on the home of her girlfriend’s mother, who has ample space and lives alone.

“We literally talked about it this morning,” Brewer said, adding that she feels lucky to have a safe place to go. “We can only imagine how screwed everyone else feels. There’s nowhere you can go to feel safe.”

Water-dropping helicopters were briefly grounded because the strong winds made it unsafe to fly. Officials didn’t immediately know the cause of the fire, one of several that broke out across the region, including another one in Orange County that prompted evacuation orders near the city of Yorba Linda.

About 355,000 power customers — estimated at about 1 million people — were in the dark in the northern part of the state as officials issued warnings for what could be the strongest winds in California this year.