DIAMOND BAR, Calif. — With the ferocious Santa Ana winds dying down, firefighters made gains today on three raging wildfires that have destroyed hundreds of homes and forced thousands of residents to flee.

Wind gusts had peaked to more than 70 mph at the height of the fires over the weekend, but by this morning they weakened to about 20 mph, the National Weather Service said.

“It’s wonderful news,” Angela Garbiso, a spokeswoman with Orange County Fire Authority, said today. “When it calms down, it obviously makes it easier for us to handle this massive undertaking.”

The fires, which have burned since Thursday night from Santa Barbara to Los Angeles and counties to the east, blackened more than 35,000 acres or 55 square miles.

In Orange and Riverside counties, the fires chewed through nearly 24,000 acres and were pushing toward Diamond Bar in Los Angeles county.

A major aerial attack on Sunday raised containment to 19 percent.

Meanwhile, a 10,000-acre fire that hit hard in the Sylmar area of northern Los Angeles on Saturday moved into the Placerita Canyon area of the rugged San Gabriel Mountains and was burning vigorously, but well outside the city. It was 40 percent contained.

The Santa Barbara-area fire that swept through tony Montecito has burned 1,940 acres and was 80 percent contained.

The cause of all the fires were under investigation, although officials said the Santa Barbara-area was “human caused,” said Doug Lannon, a spokesman with the California Department of Forestry and Fire Protection.

Lannon said the fire started in a Montecito landmark known to be a popular hangout for teenagers. He said it was possible someone was smoking in the brush or started a campfire there. Investigators have set up an anonymous tip line in hopes of getting the public’s help in finding out who started the fire.

Far away from the flames, the smell of smoke pervaded metropolitan Los Angeles. Downtown skyscrapers were silhouettes in an opaque sky and concerns about air quality kept many people indoors. Organizers on Sunday canceled a marathon in suburban Pasadena, where 8,000 runners had planned to participate.

Officials warned of another bad air day today, and classes were canceled at dozens of schools near the fire zones in Orange County.

Many evacuees began the agonizing process of making their way back to their destroyed homes.

Starting this morning, anxious residents of the Oakridge Mobile Home Park in Sylmar, where 484 homes were destroyed by fire early Saturday, will be allowed to return to inspect their property. Firefighters were able to save about 120 other homes in the community, but many were badly damaged.

Cadaver dogs had been searching the burned units to determine whether anybody perished during the fast-moving fire, but so far no bodies have been found, police said.

Tracy Burns knew her Sylmar home was gone but still wanted to get into the gated community to see what remained.

“Even those of us who know there’s nothing left, we want to go in and kick over the rubble and see if we can find something, anything,” Burns said.

Tears welled in her partner Wendy Dannenberg’s eyes as she echoed: “If I can find one broken piece of one dish — anything, anything at all.”