PROVO, Utah — Malfunctioning fireworks veered into the stands at a crowded Utah football stadium and struck members of the audience during a Fourth of July celebration, sending up to six people to the hospital, according to authorities and the event organizer.

The mishap occurred during the opening ceremonies of the Stadium of Fire show, the flagship event at Provo's annual Freedom Festival at Brigham Young University's LaVell Edwards Stadium. The fireworks were shot off inside the outdoor arena as several jets passed overhead.

Organizers halted the show for about 15 minutes while injured audience members received medical attention, Freedom Festival spokesperson Emory Cook said Friday.

As many as six people were taken to the hospital, including one with serious injuries, Cook said, adding that he did not know the severity of the other injuries nor the number of people who were struck by fireworks.

Local authorities are investigating the cause of the mishap.

Videos posted on social media show individual fireworks veering off from the cluster sent into the sky over the field and landing among rows of spectators in the stands at the outdoor arena. About 45,000 people attended the sold-out show, Cook said.

''Definitely a firework malfunctioned, but we're still trying to figure out how that happened,'' Cook said. ''All the fireworks were installed properly before the event, and they were inspected and approved prior to the show by authorities.''

Teresa Jack of Provo, who was watching the show from the field, said she saw a rocket fly over her head and into the stadium's east stands, exploding and sending up a big cloud of smoke like a bomb going off.

People in the crowd started waving to let officials know there were injuries and yelling ''stop the show'' at the speaker on stage, she said.

People were asked to remain in their seats while injured people were told to report to a medical tent for treatment, said Jack, a well-organized response she credits for preventing a stampede.

Fire department personnel and paramedics were on scene when the show started and reached the injured audience members within a minute, said Provo Fire and Rescue spokesperson Jeanie Atherton.

She said her department transported only one person to the hospital but that other victims might have gone by personal vehicles.

The event, which featured the Jonas Brothers, resumed under approval from the Provo fire marshal after the fireworks had been inspected following the accident, said BYU police department spokesperson Karen Ellingson.

The fireworks that malfunctioned inside the stadium were relatively small compared with the large pyrotechnics that are used during the show's finale, Cook said. Those larger fireworks are kept outside the stadium, he said.

The Fourth of July show was organized by Stellar Fireworks of Wichita, Kansas. Company representative Andrew Nguyen said the pyrotechnics that misfired were from a device called a repeater that fires 25 shots simultaneously.

''It blew apart and instead of the shots being oriented vertically, they became horizontal because the device had no structure,'' he said.

Nguyen added that the company has staged fireworks shows in Provo for 40 years without a comparable incident.

Jack, who went to the festival to see the Jonas Brothers, said she and her friends almost left during the finale partly because of the earlier malfunction but stayed because the display was amazing. But she said she was just as impressed with the drones as the traditional fireworks in the show, which made her wonder if that would be the better way to celebrate Independence Day.

''It might be time for us to reevaluate this tradition,'' she said.