State officials are investigating how eight people became trapped upside down on a roller coaster — some of them for more than three hours — at a festival in Wisconsin.

The roller coaster's cars got stuck near the top of a loop around 1:30 p.m. Sunday at the Crandon International Offroad Raceway. Rescue workers arrived to find eight passengers hanging upside down from their safety harnesses. Firefighters used ladder trucks to reach them, securing each one before releasing their over-the-shoulder safety bars, the Crandon Fire Department said.

It took nearly three and a half hours to get all the passengers down. One person was taken to a hospital.

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According to the fire department, a ride operator said something broke down mechanically on the coaster, which had been inspected by the state.

The state Department of Safety and Professional Services is responsible for reviewing plans for amusement parks and inspecting rides in Wisconsin. Spokesperson John Beard said in an email that the agency is investigating and dispatched an inspector on Monday to the scene in Crandon, a city of about 1,700 northwest of Green Bay. He had no further information on possible findings.