Three people sustained critical burn injuries and were transported to a local hospital, Los Angeles County Fire Department spokesman and Battalion Chief Roland Sprewell told CNN. One other person reportedly made their own way to the hospital, Sprewell added.
An initial call to 911 came in on Tuesday around 4:45 p.m. local time, Los Angeles County Fire Department Inspector Henry Narvaez told CNN.
The incident occurred in what was described as an industrial center or parking lot in Santa Clarita, where several semi-trailers had been parked, Sprewell said.
Movies are often filmed at the site, but there were none filming at the time of the explosion, Narvaez said.
A brush fire broke out an covered an acre but was extinguished by 120 firefighters and two water-dropping helicopters.