The explosion occurred about 3:46 a.m. in the 800 block of Mission Rock Road, Ventura County sheriff’s and fire officials said. Authorities had initially said the location was in the 1100 block of Cummings Road.
The Los Angeles County Fire Department was sending hazmat teams to assist in the response, the agency said on Twitter.
One of two people who were in the truck, three firefighters and an ambulance driver were hospitalized with unknown injuries, according to Sheila Murphy, a county spokeswoman. Twelve others were being for observation, he said.
The three firefighters’ boots had “spontaneously combusted” when they came in contact with the white liquid from the vacuum truck, said Rick Macklin of the Ventura County Fire Department.
Mandatory evacuations were ordered for all residents within 1 mile of 815 Mission Rock Road, authorities said. A shelter-in-place order was issued for residents within 2 to 3 miles of that location. A Red Cross shelter was open at 530 West Main Street.
Mission Rock Road was closed to all traffic until further notice, fire and sheriff’s officials said. Highway 126 was closed in both directions between Wells and Peck roads.
Briggs Elementary School was closed as a result of the incident.
The cause of the explosion was not immediately known.
Check back for updates on this developing story.