Wisconsin probes how 8 roller-coaster riders became trapped upside down for hours

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State officials are investigating how eight people became trapped upside down on a roller coaster at a festival in Wisconsin. 

It happened Sunday afternoon at the Crandon International Offroad Raceway. 

The Crandon Fire Department says the roller coaster got stuck near the top of a loop. 

Rescue workers arrived to find eight passengers hanging upside down from their safety harnesses. 

Firefighters used ladder trucks to climb up to the passengers. 

Freeing them safely took nearly three and a half hours. 

One person was taken to a hospital. 

The fire department says an operator blamed a mechanical breakdown.