The blast was reported around 4:45 p.m. in a mixed use industrial neighborhood of Santa Clarita, said Los Angeles County Sheriff's Deputy Abraham Bedoyan.
The Los Angeles County Fire Department said the explosion was reported in the 25100 block of Rye Canyon Loop, and sparked a small brush fire that burned about an acre on a grassy hillside.
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The blast was first reported taking place at a film set, but a sheriff's deputy later told KABC-TV that it happened at an industrial business, and it was not owned by a film company.
The victims suffered critical injuries - second and third-degree burns - and were transported to Henry Mayo Hospital, according to the fire department.
It was not immediately clear what caused the explosion.
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A hazmat team was also at the scene to assess the situation.
Fire spread to a grassy hillside but firefighters were able to quickly douse the flames, Rangel said. Aerial TV news footage showed fire crews at a large lot with multiple cargo containers.
Sheriff's officials advised residents to stay clear of the area about 30 miles (48 kilometers) north of downtown Los Angeles.
The Associated Press contributed to this report.