VIDEO : WATCH: Wisconsin roller coaster riders trapped upside down

Officials in the US state of Wisconsin are investigating how eight people became trapped upside down on a roller coaster at a festival; some of them for more than three hours.

The roller coaster’s cars got stuck near the top of a loop around 1:30 pm 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.