Des Moines, Iowa ? A Fourth of July fireworks shell misfired in a northern Iowa town, sending a fireball skidding down a street into a crowd of spectators and injuring 37 people, officials said Saturday.

Most of the people treated after the Friday night accident in Charles City suffered minor injuries, city fire department spokesman Eric Whipple said.

It appears there was a misfire involving 13 racks of firework tubes during the finale of the city-sponsored show, Assistant Fire Chief Dave Boehmer said Saturday.

Officials didn’t yet know why the fireworks malfunctioned, Boehmer said. Inspectors from the state fire marshal’s office in Des Moines visited Charles City on Saturday.

“It appears they went horizontally across the ground, some of them,” Boehmer said of the fireworks.

Witnesses told the Charles City Press that a large fireball veered toward the crowd gathered downtown on lawn chairs and blankets.

“It was like a bunch of little fireworks just coming toward us,” said spectator Emily Watson. “They started to explode. It was just like skating right across the street and then I saw them exploding right in the street here. … In a split second, it started coming at me.”

Brenda Schweiger said she feared for her life.

“My exact thought was, ‘This is it, we’re going to die,”‘ she said.

The city of about 7,800 people is 125 miles northeast of Des Moines, near the Minnesota state line.

Police in Riverside, Ohio, said a man lost part of his leg when fireworks went off inside his parked sport-utility vehicle, blowing the windows out.