Eight stuck upside down on US roller coaster for more than three hours

Wisconsin officials are investigating the ride failure, which required firefighters to free those trapped near the top of a loop'

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

The nightmarish incident took place on Sunday at the Forest county festival in Crandon, a city of about 1,700 north-west of Green Bay.