The children were part of a reenactment group that had gathered for a parade. During the reenactment, the cannon was shot off and a spark from the blast landed on a pouch that contained more charges for the cannon, a release from the city's Department of Public Safety said.
The pouch blew up, engulfing the three children in flames, witnesses said.
The children were transported to a local hospital. Their ages weren't reported.
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