WEST BURLINGTON (AP) — A tube of fireworks ignited prematurely during a Fourth of July display in southeastern Iowa, creating sparks that detonated other fireworks waiting to be lit and injuring four event employees, authorities said Thursday.

The accident happened shortly after 10 p.m. Wednesday, about five minutes into West Burlington’s annual fireworks show put on by J&M Displays, a Yarmouth, Iowa-based company that hosts similar events throughout the region, City Administrator Dan Gifford said.

The fireworks ignited and burned one or more of the workers, and apparently injured others as they ran for cover, he said.