BONSALL -- Firefighters herded a 118-acre brush fire of "suspicious" origin away from Monserate Hill homes and had it partially surrounded late Saturday in Bonsall, officials said.

The blaze was estimated to be 30 percent contained by 9 p.m., said North County Fire Protection District spokesman John Buchanan. Firefighters were to remain on the fire lines overnight, he said, and aircraft will return early today to continue extinguishing any hot spots.

The fire was the second to break out in the same general area Saturday. Firefighters' efforts were aided by high humidity and light breezes estimated at 10 mph or less.

Firefighters extinguished a 2 1/2-acre brush fire reported at 7:45 a.m. in the San Luis Rey riverbed to the south of Highway 76 off Via Monserate and Orange Hill, Buchanan said. Another fire broke out just after 1 p.m. about a quarter-mile east in the river bottom off Calle de Vuelta and Via Monserate, he said.

"Both fires are suspicious and under investigation," Buchanan said.

California Department of Forestry and Fire Protection investigator Gary Eidsmoe said it may have been a transient's campfire that got out of control, or it could have been something more deliberate.

"We're hoping it's not the same individual that lit the Oceanside fires," Eidsmoe said.

An arsonist set 43 fires in the San Luis Rey riverbed near Benet Road from mid-January through March 12. Detectives interviewed a transient who camped in the area, but were unable to charge him or anyone else with the fires.

Early on Saturday, firefighters thought they had a handle on the blaze they called the Vuelta fire, but it suddenly started igniting spots outside a fire-break line, causing firefighters to scramble to get it out, forestry fire dispatcher Denise Caster said.

At one point, firefighters worried the fire might take off up Monserate Hill, where one to two dozen homes dot the hillside, said fire Battalion Chief Don Stevens. Sheriff's deputies and California Highway Patrol officers went door to door warning residents to consider evacuating.

"It's not a mandatory evacuation, but it's highly, highly, highly recommended," Stevens said at the time. "It's as close to a mandatory evacuation as you can get."

Residents were told they could wait at a church off Highway 76, but no one showed up there, Fallbrook sheriff's Sgt. Ron McCracken said.

At the peak of the fire, there were 35 fire engines working with personnel that included Solana Beach and Poway firefighters, as well as six hand crews, a bulldozer, three helicopters, four air tankers and an air attack plane, Buchanan said.

By 7 p.m., firefighters were certain the homes were safe and were letting residents return to their homes as long as they did not try to get there on Highway 76, which remained closed at Mission Road and Old Highway 395 due to smoky conditions, a California Highway Patrol dispatcher said.

Fallbrook resident Lindsay Kanewischer, who showed up with her binoculars to watch firefighters, said the fire was not near her home, but it's a small community, and whenever there is any fire people get nervous.

She said they could see "big billowing smoke" near Gird Road.

"We were really worried about it jumping (Highway 76 to the north side)," Kanewischer said. "We just wanted to make sure it wasn't going to turn into a big deal."

Another resident, Meredith Coon, who lives on Alta Vista Drive, said he also came to see if there was any need to be concerned. Coon said he was in San Diego when the fire started and as he was driving up Interstate 15, he was worried it was his hill that was on fire at first.

Contact staff writer Yvette Urrea at (760) 901-4076 or yurrea@nctimes.com.