Update at 6:11 p.m.: The fire is now at 1,800 acres, with five percent contained.
"Buck" Fire [Update] is now 1800 acres, 5% contained. #BuckFire— CAL FIRE Riverside(@CALFIRERRU) August 15, 2012
Update at 6:02 p.m.: The Riverside County Fire Department's Twitter feed now has the fire at 600 acres, zero percent contained.
The Los Angeles County Fire Department has sent mutual aid.
Update at 5:52 p.m.: CBSLA is reporting one home is on fire. The fire is now at 250 acres, says KPCC's Steven Cuevas, and has been named the Buck Fire.
Update at 4:06 p.m.: The fire has ballooned to 125 acres. Riverside Fire has no word yet on how much has been contained.
Evacuations have been ordered for residents in the Riverside County community of Aguanga, after a brush fire erupted near the town and burned 50 acres. More than 200 firefighters are fighting the blaze, according to NBC-LA.
"Mandatory evacuations have been ordered for residents north of Sage Road, south of Stanley Road, east of Benton Road and west of Reed Valley Road," according to an alert from fire officials.
The Riverside County Fire Department says the fire was reported shortly before 1 p.m. Tuesday and has grown to about 50 acres. The American Red Cross has opened an evacuation center the Temecula Community Recreation Center. It's not immediately known how many residents are affected.
Three structures have been confirmed damaged, according to the Riverside County Fire Department, but no injuries have been reported.
Aguanga is east of Temecula near the Riverside-San Diego county line.
Elsewhere, a cluster of four lightning-sparked wildfires in northeastern San Diego County now covers more than 2,300 acres and more than 260 acres have burned in Joshua Tree National Park.
This story will be updated as information comes in.