A brush fire was burning early Tuesday afternoon in the Santa Ana River bottom in the Riverside County community of Jurupa Valley.
The fire burned about 100 acres after it was reported around 11:30 a.m. on the north side of the dry channel in the area of Bain Street and Limonite Avenue, just north of the Hidden Valley Nature Center. Flames were moving at a moderate rate in thick brush.
Engine and hand crews from the county and Riverside Fire Department were sent to the location.
No homes or other buildings were immediately threatened. No evacuation orders were issued.
Two Cal Fire air tankers and two water-dropping helicopters were requested.
Details about how the fire started were not immediately available.
The river bottom has several homeless encampments.