JURUPA VALLEY (CBSLA.com/AP) — Authorities called 12 ambulances Friday night to an industrial area of Jurupa Valley after dozens of warehouse workers became ill from an odor in a trailer.

The incident was reported shortly after 8 p.m. at Swift Transportation, which is a distribution center for Wal-Mart and Samy’s Club, located at 11888 Mission Boulevard, according to Cal Fire.

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Officials say 43 employees were transported to a hospital, three of whom were listed in serious condition.

The Riverside County Fire Department says hazardous material specialists determined the chemical was sodium benzoate, a food preservative that becomes a respiratory irritant when combined with moisture.

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Lisa Mann says her daughter, who works in the warehouse, told her a chemical had exploded inside the trailer. Mann said her daughter had trouble breathing after the accident.

“Nothing’s been told to none of us,” Mann said of the factory’s response.

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Firefighters say the chemical has been contained.