SANTA PAULA ( — A chemical spill sparked multiple explosions, sickening dozens and forcing nearby residents to evacuate their Ventura County homes on Tuesday.

By late afternoon, investigators were preparing to move in as the toxic smoke had diminished at the Santa Clara Water Waste Co.

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Firefighters arrived at the scene about 3:45 a.m. after reports that a vacuum truck had exploded. The truck was sitting in the middle of the facility surrounded by a white substance that was spread by the explosion. When firefighters looked down at their shoes, they saw the material sparking into flames around their feet, and quickly got away ahead of a series of explosions.

Ventura County fire Capt. Mike Lindberry told CBS2’s Randy Paige that the material on the ground was a form of organic peroxide, a highly volatile chemical that burns quickly. He said a big concern was nearby toxic chemicals, including sulfuric acid and other corrosives, that would create extremely hazardous smoke if they caught fire.

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“We had acids burning, we had wood, we had everything in the area, rubber on tires and boots burning,” Lindberry said. “The big concern was the fact that if we were to have a large explosion we don’t want people in that area.”

That meant mandatory evacuations for everyone within a mile of the plant, and shelter-in-place orders for everyone within a 3-mile radius, as well as the closure of Highway 126.

Lindberry said putting water on the fire could have caused even bigger problems, including the potential contamination of the nearby Santa Clara River. So firefighters had to wait for it to burn itself out.

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At least 37 people were treated for exposure to the volatile chemicals, with most complaining about irritated eyes and throats. All of the injured, except the truck driver, were released.