Great America introduced a new adventure to 24 thrill seekers Monday — their high-speed Invertigo roller coaster that ground to a torturous halt near its zenith and remained stuck for hours in the sweltering afternoon heat, suspending riders as high as 80 feet in the air before they were rescued by firefighters.

The Santa Clara amusement park's Invertigo roller coaster, which ordinarily specializes in turning people upside down, instead got stuck on the tracks, stranding two dozen people for an afternoon just as they began the adrenaline-filled ascent to the top of the ride. Park officials and state investigators are trying to determine why the ride malfunctioned. The coaster stopped about 1 p.m., leaving the riders strapped in their seats, legs dangling in the air while firefighters hoisted basket-topped ladders to retrieve them one by one. It took more than four hours in 95-degree heat before the last relieved patron reached the ground.

Two ladder trucks — one with a basket that can accommodate two or three people and is capable of reaching a height of 110 feet — brought the riders down, ending the effort shortly before 6 p.m