AVON, Colo. (AP) -- Officials say nine people suffered minor burns during an accident at a fireworks show in Colorado.

Fireworks in Avon, Colorado (YouTube)

Virginia Egger, the town manager in Avon, says a malfunction caused a fireworks shell to explode in its tube rather than firing into the sky Friday night. She says the misfired shell caused a rack of shells to tip, causing two or three shells to go off toward the crowd.

The accident occurred about 17 minutes into the 23-minute fireworks show over Nottingham Lake, bringing the event to a halt. The annual event attracts about 20,000 people.

Jane Imber tells NBC News that there wasn't a lot of room in between groups of people, so people couldn't get up and run.

The cause of the malfunction is under investigation.

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