Firefighters are battling a blaze that burned about 250 acres of vegetation in Sycamore Canyon Saturday, the Riverside Fire Department said.
The blaze is burning through a remote area adjacent to a previous fire from July, the department said. It was 40 percent contained Saturday evening.
"Forward progress has been stopped," fire officials said in a written statement.
The slow-moving fire was first reported at about 2:58 p.m. at 40 acres and it grew to at least 100 acres by 3:50 p.m., authorities said.
An hour later, the fire had grown to consume about 250 acres and was still expanding, according to Riverside Fire Department spokesman Brian Guzzeta.
There was a mild threat to nearby commercial and residential buildings in the area of Speyside Road, but no evacuation orders were issued, Riverside Fire Chief Bruce Vanderhorst said.
Over 130 firefighters responded to battle the blaze, along with three air tanks, two dozers, a helicopter and 25 engines, Guzzeta said.
Speyside Road was closed at Perthshire Place and residents were asked to avoid the area.
Jeff Werner told KTLA ke kept sprinklers running around the perimeter of his property as a precaution.
It's unclear what ignited the fire. No injuries or structure damage had been reported.
Check back for updates on this developing story.
KTLA's Brian Day contributed to this report.