Fire officials said crews near the Pala Casino expect to contain a roughly 120-acre fire by Monday morning.
The blaze, which damaged three homes, started around 3 p.m. Sunday and prompted the California Highway Patrol to close Highway 76 between Interstate 15 and the casino, but was reopened shortly before 8 that night.
Cal Fire Capt. Nick Schuler said the fire was 15 percent contained, and the rate of growth had slowed, but Pala Norte Road was evacuated, as the blaze had the potential to grow to 500 acres.
More than 200 firefighters used 26 vehicles, including a bulldozer, and four airplanes and three helicopters dropped water from the nearby San Luis Rey River, Schuler told the San Diego Union-Tribune.
He said major electrical transmission lines were threatened, but San Diego Gas & Electric did not report any outages in the North County.
The cause of the fire was not immediately known. "It wasn't lightning, and I've pretty much ruled out the power lines nearby," Battalion Chief Jim Garrett told the Union-Tribune. "I can tell you it's a human cause. It's too early in the investigation to say it was arson."
Another brush fire broke out around 1:50 p.m. Sunday in the area of Cedar Creek Falls, east of San Diego Country Estates, near where a lost hunter accidentally started the deadly Cedar Fire in 2003, was contained to three acres and no structures were damaged, according to dispatchers with the U.S. Forest Service.
In Santee, a small spot fire around 3 p.m. Sunday burned for about 20 minutes at an area along Highway 67 in the construction zone for the new Highway 52 interchange, said a dispatcher with the Heartland fire dispatching agency. Again, no one was hurt and no damage was reported.