SANTA PAULA, Calif. (KABC) -- A fire continued to burn and explosions were still occurring at a wastewater facility near Santa Paula agricultural fields several hours after a vacuum truck exploded overnight.Authorities responded to the 800 block of Mission Rock Road at 3:45 a.m. Tuesday. Approximately 1,000 gallons of organic peroxide spilled after the rear of the vacuum truck exploded.Hazmat teams from Ventura County and L.A. County fire departments responded to the scene. A large plume of smoke from the fire was going into residential areas.Fire officials said they were dealing with a 300- to 400-foot radius of white substance, identified as organic peroxide. When the material dries, it crystallizes and catches fire."As this liquid began to dry out, the companies on scene noticed that it was very unstable and reactive, and as they stepped on it or tried to move their engine, it would spontaneously ignite under the tires of the engine or their boots," said Ventura County Fire Capt. Mike Lindberry.Because the material ignited spontaneously, firefighters were forced to retreat, officials said. Firefighters were allowing it to burn off because officials were very concerned about the water going into the Santa Clara River.A mandatory evacuation was ordered for all residents within a mile of 815 Mission Rock Rd, and a "shelter in place" was ordered for residents within two to three miles of the location. The evacuation distance was later reduced to 0.5 mile. A Red Cross shelter location was open to residents at 530 W. Main St. in Santa Paula.Two workers were injured during the early part of the incident. One of the workers was transported to Ventura County Regional Medical Center in unknown condition, and the other went to the hospital on his own later, officials said.Ten firefighters were also taken to an area hospital for precautionary measures, including at least three due to flames on the bottom of the firefighters' boots.Hospital officials say 37 people were treated as a result of the explosion and fire. All were expected to be released, except the driver of the truck that exploded, who suffered traumatic injuries.All lanes of Highway 126 were shut down between Peck and Wells roads for more than six hours. Mission Rock Road was also closed.Briggs Elementary School was closed for the day. All students were evacuated to Olivelands Elementary School, where parents were able to pick up their students.The cause of the initial explosion has not been determined.Residents with questions can call a public information hotline at (805) 465-6650.