More than 200 firefighters with help from water-dropping helicopters and an air tanker had the blaze in the San Gabriel Mountains 85 percent contained, Monrovia city spokeswoman Jennifer McLain said.
"The fire is laying down," McLain said at an afternoon news conference. "You don't see the flames."
Power equipment used by a gardener working in a backyard sparked the fire Saturday, city fire Chief Chris Donovan said. The gardener was clearing brush in anticipation of fire season.
Flames spread to a hillside behind the home and the fire soon surged to about 125 acres, sending a huge smoke cloud that could be seen across the San Gabriel Valley.
More than 300 houses were under evacuation orders at the fire's peak. Nearly 100 remained Sunday morning, but by late afternoon all residents had been allowed to return home.
Firefighters struggled to surround the fire amid thick, dry brush on steep terrain, and one of them suffered a heat-related injury, Donovan said.
There were no reports of other injuries or damages, and no estimate on when firefighters would have the blaze surrounded, though they were expected to work at least through the night.