A malfunctioning firework caused a dramatic Fourth of July pyrotechnic disaster in Simi Valley that injured dozens of people, fire officials concluded in a report released Thursday.

A five-inch-wide firework shell failed to leave its mortar tube and exploded inside, sparking a chain reaction that knocked down the display and sent debris and firework projectiles flying toward about 10,000 spectators watching hundreds of feet away.

DRAMATIC VIDEOS OF ACCIDENT

The incident was investigated by Cal/OSHA, CalFire and the Ventura County Fire Department.


“All of the information we have on this incident indicates that there was simply a tragic malfunction that resulted in the explosions,’ said Ventura County Fire Chief Mark Lorenzen. “As a result, we will be reviewing the state fireworks policies to see if additional local measures might be warranted.”

Video footage showed fireworks exploding at ground level and into the crowd as people screamed and ran for cover. Police said after the initial chaos, the crowd left in an orderly manner.

Photos: Simi Valley fireworks explosion

“There was a big boom. Everybody started running down the street. People were screaming,” Justice Allen, 17, of Simi Valley told the Times after the incident. “Everybody was just terrified. People hid in bushes.”


There were 28 people injured, with the victims ranging in age from 8 to 78 years old. Twenty people were taken to local hospitals with non-life threatening injuries. Most of the injuries were described as shrapnel-like injuries or burns.

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Joseph.serna@latimes.com

@josephserna