A fire erupted Friday in the Santa Ana River bottom in Riverside, quickly blackening three acres but posing no immediate threat to homes.
The non-injury blaze was reported around 2:35 p.m. in the vicinity of Anza Narrows Park, just off Rio Rancho Way.
Riverside firefighters requested assistance from Cal Fire to contain the flames, which were being fanned by light winds in the dry riverbed, according to reports from the scene.
A Cal Fire water-dropping helicopter was making drops on the blaze.
There was no immediate indication of how the fire started, but three people seen leaving the location where the flames were initially reported were detained for questioning, authorities said.