Five people were hurt, with two of them suffering serious injuries when a theme park ride at the North Carolina State Fair jolted back to the starting point as riders were disembarking, according to authorities and witnesses and reported by NBC News.

Authorities said it was too early to tell what caused the malfunction, though they were interviewing witnesses and trying to find video of the accident. The ride, called the Vortex, had previously passed all inspections.

The ride was closed after the accident, but the state fair continued. The state agriculture commissioner said he was so confident in the safety of the other rides that he would allow his own grandchildren to get on them.

Caleb Norris had just stepped off the ride on Thursday when he heard a crashing sound, Caleb Norris told WNCN, the NBC affiliate in Raleigh. He turned around and saw two people facedown and the ride operator had fallen to his knees in tears.

"It just sounded like a bunch of stuff hitting metal," Richard Gephart, another witness, told WNCN. "And that was it, there was no screaming."

The ride had been briefly shut down on Monday night due to a malfunctioning switch, which is part of the mechanism that locks riders into their seats, according to Tom Chambers, an inspector with the state Labor Department. The switch was repaired and inspectors checked it out, and then the ride was allowed back into operation.

Two of the injured riders were released from the hospital on Friday.

At least 17 states don't regulate amusement park rides, according to NBC News. North Carolina is one of the states that does regulate them. According to a spokeswoman for the state Labor Department, the Vortex is inspected for safety three times a day during the fair.

This isn't the first time an injury occurred at the state fair. In October 2002, a worker was killed at the fair when the gondola on a different ride, the Banzai, struck him in the head.

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News coverage of the accident.