Three people remain hospitalized in good to critical condition after a ride at the North Carolina State Fairgrounds in Raleigh started to move as riders were exiting, according to authorities.
The first call to 911 came around 9:17 p.m. Thursday after a ride called the "Vortex" restarted, Wake County Sheriff Donnie Harrison said at a news conference Thursday night, citing preliminary information.
Eyewitnesses reported seeing passengers thrown off the ride while others were holding on.
"There were actually some people that were still, I think, strapped in and holding on, really hanging on for their lives," Max Byrn, 13, told ABC News Radio. "But they were falling like raindrops. It was really crazy."
The Vortex is a pendulum ride that flips passengers upside down as it heads toward the sky.
Ambulances initially rushed five victims, ranging in ages from 14 to 39, to a nearby hospital, Debbie Laughery, vice president for public relations at WakeMed Health and Hospitals, told ABC News.
Two of the injured were released overnight, Laughery said.
Sheriff Harrison said some of the victims were from the same family, but he wasn't sure of the exact relationship. The other injured person was the ride's operator, Harrison said.
No information was given on the kinds of injuries sustained.
Fair officials and Department of Labor officials are working to determine the cause of the accident, fair spokesman Brian Long said in a news release. A switch problem had been fixed Monday, officials said, but they didn't know yet whether it was related to the accident.
The accident occurred shortly before the fair was shutting down for the night.
Max said he had just gotten off the ride and turned around when he heard screaming. The teen said the ride was upside down when people began falling.
"People were screaming and a lot of people were in pain. Family members actually ran away, like they couldn't bear to look at it. They were dropping about 30 feet high up in the air," he told ABC News Radio.
Max said one person landed head first on the ground and "was completely knocked unconscious" from the fall.
Eyewitness Caleb Norris said, "We could see at least three people just laying there non-responsive."
Police questioned 35 to 40 people at the scene, authorities said.
Sheriff Harrison said everyone is working hard to make sure all the rides at the fair are safe.
"As sad as it is, we want people to come out and have fun," he said. "It'll be safe. We'll do everything we can to make it safe for the families that come and the main thing is to keep those that got hurt tonight in our prayers."
A ride operator at the fair died in 2002 when he was struck by the ride while it was still in operation, The Associated Press reported.
The North Carolina Labor Department told ABC News the Vortex is supposed to be inspected for safety three times during the annual fair.
"They will be looking at the diagnostics, all the safety systems and any piece of that ride to determine if it was indeed a malfunction of the ride," Labor Department spokeswoman Dolores Quesenberry said.
The fair is expected to reopen today as scheduled, Long said in the press release. The fair is scheduled to end Sunday, according to its website.
"The ride was manufactured by Technical Park International of Italy. This is the first time this Vortex ride has been at the N.C. State Fair," according to the release. "There are two Vortex rides on the fairgrounds. The other Vortex, located on the new midway, has been on site for many years and is manufactured by Fabbri of Italy."
The association that represents carnival operators told ABC News that Americans took more than 1 billion rides a year and that each year 13,000 people were injured and visited an emergency room.
That's a higher rate than at theme parks, which see 1.7 billion riders and just 9,200 injuries.