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 today.

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 Beamer said Saturday.

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

“It appears they went horizontally across the ground, some of them,” Beamer 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,” spectator Emily Watson said. “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.

Elsewhere, 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.

A 6-year-old girl in Bayville, N.Y., suffered second-degree burns when fireworks landed in her lap, police said. Investigators said it wasn’t immediately clear who launched the fireworks but said the child wasn’t at a public pyrotechnics display.

A 3-year-old boy in Leominster, Mass., suffered serious burns after his father shot off fireworks that went awry, authorities said. The 37-year-old man will probably be charged with illegal possession of fireworks, police said.

In Port Huron, Mich., a 51-year-old man was critically injured when he was struck in face by a mortar-type firework, the St. Clair County sheriff’s department said. Officers said the man was placing the firework in a tube when it ignited.