Firefighters gain upper hand on 400-acre Sierra fire burning near buildings in Fontana

A 400-acre brush fire was temporarily threatening some buildings in Fontana near the Jurupa Hills Regional Park area on Sunday.

The fire, which is being referred to as the Sierra Fire, was first reported at about 3:30 p.m. near Sierra Avenue, south of the I-10 Freeway, according to San Bernardino County Fire Department officials. 

It quickly grew from just one acre to 40 acres by 4 p.m. and again jumped to 350 acres by 6:30 p.m., prompting a second alarm response from firefighters including support from Riverside County Fire Department. 

At the latest it is 80% contained, according to San Bernardino firefighters. 

The fire is spreading southeast "with moderate side slope expansion to east," firefighters said. 

Crews were previously set up in front of homes in the area in the event that the fire moved towards them, but they say that the threat to structures has been mitigated.

As a result of the firefight, Fontana police have shut down Sierra Avenue at Jurupa Avenue to the public. It is expected to be reopened as soon as 10 a.m. Monday morning. 

Crews say that structures are threatened by the spreading flames, but no evacuation orders have yet been issued. 

Because of the large fire, the South Coast Air Quality Management District issued a Wildfire Smoke Advisory through Monday afternoon. 

The advisory was issued for parts of San Bernardino and Riverside Counties, including the communities of Fontana, Jurupa Valley, Bloomington, Rialto and Colton. 

People living in those areas are advised to remain indoors with windows and doors closed. Officials advise that people should avoid vigorous physical activity and to run air conditioning while the smoke continues to linger.