Riverside fire officials said the fire, dubbed the Jerry Fire, started out in the area of Gilman Springs Road, between Highway 60 and Jack Rabbit Trail at approximately 1:02 p.m. Officials originally had the fire burning through 200 acres.
The first crew to arrive spotted four separate fires one mile apart and had already burned through one acre each, threatening nearby structures. As many as 15 homes on Gilman Springs Road threatened were placed under evacuation orders.
Structures along Gilman Springs Road appeared to be safe from danger, but a threat to utility infrastructure in the area remained.
The blaze was moving at a moderate rate of speed with more than 200 firefighters attempting to extinguish it.
By 6:15 p.m., fire officials said the blaze had burned through 522 acres, with containment reaching 20 percent and forward rate of spread stopped.
Gilman Springs Road was closed between Alessandro Boulevard and Old Golf Course, and at Gilman Springs at Sanderson as crews worked to extinguish the fire.