Firefighters from the Riverside Fire Department battled a heavy vegetation fire near the Santa Ana River bottom Sunday.
The fire was reported just before 3 p.m. Sunday behind the Riverside Public Utilities water treatment plant, according to the fire department.
The 20-by-20-foot spot of heavy vegetation was burning at a slow rate of spread with no threat to infrastructure.
Fire crews hiked to the scene and extinguished the fire around 3:50 p.m.
No injuries or damage to buildings were reported.
The cause of the fire was still under investigation.