Crews with the Riverside County Fire Department, Cal Fire and the Corona Fire Department were on the scene of the fire, which was first reported shortly after 2 p.m.
Air tankers and water-dropping helicopters from Hemet-Ryan Airport reportedly halted the fire's forward rate of spread by 4 p.m.
Fire officials declared the blaze 75 percent contained by Monday evening.
Sheriff's deputies and California Highway Patrol officers shut down Terramor Road between Temescal and Crestley Drive for public safety and to give emergency crews freedom to move.
A fire captain fell ill from heat exhaustion amid triple-digit temperatures and was taken to Corona Regional Medical Center for treatment. He was in stable condition and not expected to remain hospitalized overnight, according to a battalion chief.
The fire approached buildings in the 24800 block of Terramor Road, but none were impacted.
There was no word on what triggered the blaze.
DEVELOPING: We will add more details to this report as they become available.
The City News Service contributed to this report.