By Marty Graham

SAN DIEGO (Reuters) - California firefighters battled to contain a brush fire on Monday that has damaged or destroyed at least 30 homes, forced dozens of others evacuated and claimed one life east of San Diego near the U.S.-Mexico border.

The body of an unidentified man was found on Monday in the charred rubble of a house after authorities said they were searching for an 82-year-old man who resides in the area and was reported missing.

The California Department of Forestry and Fire Protection declined to immediately confirm that the missing man turned up as a fatality.

But a neighbor who spoke to Reuters by telephone, Bob Gookin, said sheriff's deputies have been inside the scorched ruins of the missing man's home, and he believes they had found a body.

"His truck is pretty distinctive and it's parked out front," Gookin said. "It's the house down from us, next to the Boot Hill Ranch."

The so-called Shockey Fire erupted near the Campo Indian Reservation in southeastern San Diego County at midday on Sunday and has scorched at least 2,000 acres of dry brush, authorities said.

By Monday afternoon, crews had managed to carve containment lines around 10 percent of the fire's perimeter, CalFire incident manager Rick Vogt said.

The origin of the fire was under investigation, but Blanca Mercado, a spokeswoman for the California Department of Forestry and Fire Protection, said officials are looking into the possibility that the blaze started in Mexico.

Property losses from Sunday in the fire zone, about 50 miles east of San Diego, are estimated at more than 20 houses and 15 other buildings destroyed, with about 10 other dwellings damaged, Mercado said.

The overall area is sparsely populated with clusters of homes and ranches scattered throughout.

Mercado said Sunday evacuation orders remain in effect and fire managers were expecting hot, dry Santa Ana winds from the desert to gust up to 25 miles per hour later in the day.

Gookin, who breeds Clydesdale horses with his wife on their property, said he returned to his ranch after a close call with the flames.

"The fire went right past us," he said. "We drove our golf cart up and watched it come up over a ridge to the west. ... It went down through the church camp across the road and burned up the house on Boot Hill Ranch and then on down the road."

As of Monday, 18 fire crews consisting of nearly 400 personnel were assigned to the blaze, along with six airplane tankers, six water-dropping helicopters and five bulldozers, Mercado said.

A local high school was turned into an emergency shelter for evacuees, but 50 to 60 residents displaced by the fire turned up instead at the Golden Acorn Casino to wait out the blaze, casino employee Diana Shea said. The casino parking lot was being used as a staging area for fire crews.

"We canceled bingo and put people in the bingo room," Shea said. "It's cool and comfortable." (Additional reporting by Steve Gorman; Editing by Doina Chiacu and Eric Beech)