Cal-OSHA's preliminary findings point to a malfunction in the lift chain of one of the cars, which caused the roller coaster to stop.
"There's something that definitely occurred with the lift chain, which is one of the mechanisms that takes the train that the guests sit in up the lift till," Great America spokesperson Jim Stellmack said.
That malfunction caused the train to stop abruptly with 24 riders stranded between 40 and 80 feet off the ground.
Stellmack says that is when safety procedures and systems kicked in.
"Our ride operator hit our emergency stop button but the ride also did stop itself," he said. "Our rides are inspected every morning so that ride did in fact go through its daily safety inspection and was cleared to run."
The ride will be closed for two months.
Cal-OSHA inspectors were on the scene Tuesday morning. A spokesperson says they will dismantle the failed mechanism and send it to the lab for structural evaluation. Inspectors will also interview riders who were stuck on the Invertigo for four hours.
"I was scared because it took a while and then police officers and fire department started coming and because I'm kind of scared of heights," rider Janice Chan said.
Fire fighters could not just unbuckle the riders for fear they might slide out and fall, so they strapped each passenger to the seat, rappelled them down to a bucket and then lowered them to the truck.
Santa Clara Deputy Fire Chief Augie Wiedemann says his firefighters have drilled for just such an accident. He says everything went like clockwork.
"We used our experience with technical rescue and then we brought in specialized equipment, the ladder trucks and the baskets," Wiedemann said.
The Invertigo suffered a similar malfunction April 19, 2000.