A fast-moving brush fire erupted in the Santa Ana River bottom Tuesday, torching at least 20 acres of dry vegetation as air tankers thundered overhead and firefighters raced to keep the blaze from exploding further.

The so-called Bain Fire broke out around 11:22 a.m. near Bain Street and Limonite Avenue in Jurupa Valley, according to Cal Fire.

Flames tore through thick brush and heavy fuels at a “moderate rate of speed,” triggering a massive firefighting response on the edge of Riverside and Jurupa Valley.

By Tuesday afternoon, officials had deployed roughly 100 personnel to the scene, along with 22 engines, two helicopters, two bulldozers, two water tenders and four hand crews, according to Cal Fire incident data.

Firefighting aircraft repeatedly swooped low over the river bottom, with at least one tanker seen dropping bright red Phos-Chek fire retardant, pictures from ABC7 showed.

Officials said numerous air tankers from across California had been mobilized to assist with suppression efforts “as conditions allow.”

Evacuations were underway by around 12:50 p.m., according to CBS Los Angeles, though officials had not yet released details on which areas were affected.

The blaze was burning near the Hidden Valley Nature Center in the dry river channel area, where crews were forced to push through dense vegetation to reach parts of the fire, according to ABC7.

No homes or structures were immediately threatened earlier in the incident, though fire officials warned the blaze had the potential to spread to roughly 80 acres if left unchecked, ABC7 reported.

However, Arlington Avenue between Crestview and Western was shutdown on the Riverside side of the river bottom as firefighters battled the blaze, according to Cal Fire.

Officials have not determined what sparked the fire.

The fire comes just a day after another wildfire erupted in the Simi Valley area of Ventura County.

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