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.
Taken a little while ago from the backyard. #TerraFire pic.twitter.com/tQvrpEqiDw
— kim yi dionne (@dadakim) August 7, 2018
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.