Aided by rainfall, fire officials expected to have the Santiago Canyon Fire 100% contained by late Friday.
About 870 fire personnel remained at the scene of the brush fire, which blackened 8,800 acres this week. They were watching for flare-ups that could reignite the blaze, said Gary Layman, a spokesman for the Orange County Fire Authority.
"Our objective now is mop up and patrol," Layman said.
At times, the fire came within 50 feet of homes in Foothill Ranch. Homeowners there had spent several anxious days watching the fire burn in the nearby hills but there were no evacuations. No homes were damaged.
Layman said the number of firefighters was expected to be down to about 100 by today.
Officials have estimated the cost of fighting the fire at about $1 million, most of which will be borne by the state, which manages the land.
The fire was started by lightning Monday. At one point this week, 50-mph winds caused embers from the blaze to jump the Foothill Transportation Corridor, starting several small spot fires.