The park said the ride suffered a problem with its lift chain, but that no one was ever in any immediate danger.
State investigators are back in Santa Clara at Great America's Invertigo roller coaster today, a day after the ride malfunctioned and locked up, prompting a near five-hour rescue operation to remove 24 trapped riders.
It's not yet clear how long the investigation will take, said Erika Monterroza, spokeswoman for the California Division of Occupational Safety and Health. The roller coaster is closed indefinitely.
Inspectors from the agency's elevator, ride and tramway unit will take the ride apart and potentially send away mechanical parts for analysis, Monterroza said. They will interview riders, operators and other Great America personnel and examine servicing records and other safety data for the roller coaster.
The ride's Japanese manufacturer will likely be involved in the probe into what caused the malfunction as well, Monterroza said.
"Really what they're looking for is why the ride failed," Monterroza said.
A preliminary investigation indicates that the ride's lift chain malfunctioned, she said. The lift chain pulls the train up the coaster's tracks.
The Invertigo roller coaster is unique because riders' feet dangle below them as they are taken in loops at speeds of up to 50 mph.
It took about 50 firefighters from from San Jose and Santa Clara nearly five hours to rescue the passengers from the ride, which was supposed to last just 70 seconds.
Images from news helicopters above the scene showed dozens of people stuck on the ride several stories above ground. The people on the lower end were at least 40 feet off the ground, with the people on top another 40 feet or so higher.
Shannon Brown was stuck on the ride for three hours, about seven stories up.
"There was a lot of noise, parts went flying. A big, heavy piece of metal went flying," Brown said, with a chuckle. "It gave a pretty rough stop -- knocked my glasses off."
Brown wasn't injured during the ordeal, but he said it was pretty tough to bear.
"That was the worst part. Because you're leaning forward for three hours." Brown said."That was uncomfortable, that hurt."
Brown's wife and children waited on the ground during the rescue.
"I was trying not to be scared, for the kids." Brown's wife, Renee said.
The park said no one was ever in any immediate danger. They said fixing the ride was priority No. 2 and that getting the rider safely off and back on terra firma was priority No. 1.
Half of the riders were stuck leaning back and the other half were leaning forward in their seats with their legs dangling.
Some of the passengers could be seen holding bottles of water.
The passengers at the very bottom of the ride were tended to first by rescue crews on a cherry picker. Fire Capt. Scott Kouns said the good news is that the riders weren't upside down, although they are at a steep angle.
"They're sitting upright," he said. "They're not hurt, there's no injuries."
It was a hot day in the Santa Clara with temperatures in the 90s. Any length of time trapped on a roller coaster would be uncomfortable, to say the least, and it took at least an hour to get the first person off the ride.
Fire crews on cherry pickers took passengers off their seats one by one. As soon as two people were off-loaded they were lowered to the ground. Kouns said that to release the riders' harnesses, which come down over their shoulders, two pins have to be released simultaneously.
Invertigo is North America's first inverted face-to-face roller coaster.
All passengers were taken down without any snags and, once on the ground, were given refreshments.
"They're being fed and drinks are available to them," Kouns said. "They're being accommodated quite nicely by the Great America staff here."
"There are people out there laughing, carrying on and talking about their experiences," he said as the rescue was taking place.
Many of those stuck on the ride could be seen swinging their legs back and forth as they waited to be rescued.
The Invertigo consists of seven-car train that takes riders upside down six times, to heights of up to 161 feet, in one minute and 10 seconds, according to Great America's Web site.
Normally Cal-OSHA is not called in for incidents in which nobody is injured, Monterroza noted. However, the agency keeps a particularly close eye on amusement park rides, she said -- both the portable kind that pop up at county fairs and permanent ones like those at Great America.
"We haven't been advised of any injuries, other than people's legs falling asleep," she said.
Monday was not the first time emergency crews have been called to the park: