LOS ANGELES — Firefighters, aided by diminishing winds, were taming a wildfire Saturday that damaged or destroyed more than 30 structures along the northern edge of Los Angeles and sent a blanket of smoke across a swath of neighborhoods.
Officials say the blaze in the city’s San Fernando Valley hadn’t grown significantly since Friday, and ground crews were tamping down lingering hot spots. However, thousands of people remained under evacuation orders, and authorities warned the potential for flare-ups remained.
Los Angeles Fire Department spokesman Brian Humphrey said the bulk of the fire had moved away from homes and into rugged hillsides and canyons where firefighters were making steady progress in slowing its advance. Television footage showed plumes of smoke rising from the area but no walls of towering flame, as a water-dropping helicopter moved in to dump another cascade on the blaze.
One man who tried to fight the blaze died of a heart attack, but no other injuries were reported.
‘‘The bulk of the fire has moved toward wildland,’’ Humphrey said.
Firefighters worked under sunny skies, but air quality was poor as smoke dispersed over much of greater Los Angeles. Air quality officials urged people to limit outdoor activities.
East of Los Angeles, firefighters were also gaining ground on a blaze that ripped through a Riverside County mobile home park, destroying dozens of residences. In Northern California, the lights are back on for 98 percent of customers who lost power when Pacific Gas & Electric switched it off in an effort to prevent wildfires.
Some 100,000 residents were ordered out of their homes because of the wind-driven wildfire that broke out Thursday evening in the San Fernando Valley. It spread westward through tinder-dry brush in hilly subdivisions on the outskirts of the nation’s second-largest city.
Interstate 5, the main north-to-south corridor in the state, was shut down for much of the day Friday, choking traffic until finally reopening.
The smoky scent spreading through much of Los Angeles was a reminder of the threat of a fire season just beginning.
The region has been on high alert as notoriously powerful Santa Ana winds brought dry desert air to a desiccated landscape that only needed a spark to erupt. Fire officials have warned that they expect more intense and devastating California wildfires due, in part, to climate change.
Fire danger remained high for much of Southern California, with warnings in place for large swaths of Ventura and Santa Barbara counties west of Los Angeles.
The cause of the Los Angeles blaze wasn’t immediately known, though arson investigators said a witness reported seeing sparks or flames coming from a power line near where the fire is believed to have started, said Peter Sanders, a spokesman for the Los Angeles Fire Department.
A Sylmar man, Robert Delgado, said he saw flames under a high-voltage electrical transmission tower near his home at around the time the fire broke out, KABC-TV reported.
Southern California Edison said it owns the transmission tower shown on KABC-TV, but a spokeswoman would not confirm that was where the fire began. The utility said it could take a long time to determine the cause and origin of the fire.
Jonathan Stahl was driving home to Valencia when he saw the smoke and immediately diverted to a mobile home park in Sylmar where his grandmother and aunt live together.
The park had been nearly wiped out in 2008 when one of the city’s most destructive fires leveled 500 homes.
Stahl helped his grandmother, Beverly Stahl, 91, who was in her pajamas, and his aunt to pack clothing and medication and take their two dogs. They saw flames in the distance as they drove away.
‘‘We just packed up what we could as fast as we could,’’ Stahl said at an evacuation center at the Sylmar Recreation Center, massaging his grandmother’s shoulders as she sat in a wheelchair with a Red Cross blanket on her lap. ‘‘If we’d stuck around, we would have been in trouble. Real big trouble.”