The Riverside County blaze known as the Opera fire grew rapidly from about 10 acres when first reported at 3:30 p.m., to more than 1,350 acres and still growing by late evening. It was threatening homes and a radio tower in the Box Springs mountain area, but no homes had been reported damaged.
At one point, firefighters said they had to ground their aircraft, used for dropping water and fire retardant, because of reports of drones flying in the area, creating a potential hazard. The helicopters were later seen returning to the skies.
The blaze broke out around 3:30 p.m. in the Highgrove community located just north of Riverside, at Opera Loop and East Palmyrita Avenue.
Firefighters said it moved quickly because of strong winds. It is burning in light fuels.
No structures have been damaged yet, but some are threatened by the blaze. No word yet on a containment estimate.
The winds that drove the flames died down around 8 p.m., but darkness also provided challenges for firefighters.
The blaze was one of several brush fires reported around Southern California on Sunday.
A blaze in the Cajon Pass, called the Tower Fire, was estimated at 200 acres, with about 20 percent containment Sunday evening, officials said.
Another fire in Temecula broke out around 2 p.m. near Via Santa Rosa and Via Vaquero Road and was last reported at five acres, with 112 firefighters engaged in the battle. It was burning in an area described as holding medium-to-heavy fuels and avocado fields.
Just south of Corona, the Jameson fire, on the 23200 block of Jameson Road, was reported around 6:30 p.m. in the hills west of Temescal Valley. By late Sunday, it was around 15 acres with 25 percent containment. It was relatively close to a residential neighborhood, but there have not yet been reports of structure damage.