Foothill communities are on high alert after a handful of brush fires broke out across Southern California this week.

Hundreds of firefighters battled blazes in Camp Pendleton, Walnut and Camarillo, where 55 homes were placed under voluntary evacuation.

Smoke from the Camarillo fire spread Tuesday to northern Los Angeles County, casting a brown hue over the San Fernando and Crescenta valleys and prompting alarmed calls from residents, officials said.

"We got about 200 [calls] even though there were no fires in the La Crescenta, La Cañada and Montrose areas," said Los Angeles County Sheriff's Capt. David Silversparre, commander of the Crescenta Valley Sheriff's Station. "One was as specific as, 'There is a fire in Pickens Canyon.' There wasn't. It was just smoke from the Camarillo fire."

The CV Sheriff's Station on Tuesday night deployed its Arson Watch squad, a community group that canvasses fire danger zones looking for suspicious activity and smoke. Volunteers patrolled Lopez Canyon, Kegel Canyon, Little Tujunga Road and the burn areas in La Crescenta and La Cañada.

"We are looking for suspicious cars parked in [hot spot] areas," Arson Watch member Paul Dutton said. "We are looking for people in areas they shouldn't be in. We are looking for lights on the mountains that shouldn't be there."

The 2009 Station fire, which triggered multi-day evacuations for hundreds of foothill homes, is fresh in residents' minds, Dutton said.

"Once I personally smelled the smoke [Tuesday], it brought all those feelings right back again, and I got very anxious about it," Dutton said.

Los Angeles County firefighters responded Tuesday to a call regarding a fire in Lopez Canyon, northwest of Hansen Dam, said Stephanie English, community services liaison with the department. But firefighters found only smoke from the Camarillo fire trapped in the canyon, she said.

There have been numerous fires in Los Angeles County in recent weeks, English said, and responders remain on high alert.

"Our patrols are out looking, and during intense weather, high winds or extreme heat, we do augment our staffing," English said. "We have extra firefighters, and we may even assign strike teams to be in position in the event that there is a fire."

Residents should clear brush from their properties, officials said, and be vigilant of suspicious activity.

"Just be observant of anybody that doesn't belong," Arson Watch leader Gary Jaegers said. "It doesn't hurt to call the station about something suspicious and let them check it out."