The Coast Guard says the mishap occurred minutes before the scheduled opening of the Big Bay Boom show, causing a display that was planned to last nearly 20 minutes to burn up all at once.
Guard spokesman Rich Dann tells U-T San Diego he's never seen so many fireworks go off at one time.
Show producer Garden State Fireworks has apologized, saying they were working to determine what "caused the entire show to be launched in about 15 seconds."
About 50,000 people were estimated to have been in attendance.
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