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Simi Valley Fourth of July mishap caused by malfunctioning firework

People are being treated at a triage following a fireworks mishap in Simi Valley on Thursday, July 4, 2013.

July 5, 2013 12:00:00 AM PDT
The Fourth of July fireworks disaster that injured dozens of spectators in Simi Valley was caused by a malfunctioning firework, according to a report released by the State Fire Marshal.

The report says the unplanned explosions were the result of a malfunction. The report explained that a firework failed to function as designed and the shell went off inside a mortar tube. That resulted in an explosion that triggered others.

The blasts sent debris from the fireworks, the racks holding them and the mortar tubes in all directions, injuring 28 spectators.

The report concluded the display was properly designed and set up. It also said Simi Valley police ruled out criminal activity or intent as a cause.