Riders and witnesses of the partial derailment of the Ninja roller coaster at Six Flags Magic Mountain said they heard loud cracks followed by screams just as the accident occurred Monday evening.
Jeremy Ead was on the famous thrill ride about 6 p.m. when a tree branch fell onto the tracks, causing the first car to derail, he told KCBS-TV Channel 2.
"We were going across one turn, and all of a sudden a loud noise happened," Ead told the station. "I ducked down just in time. A hard branch hit me in the head. I was there bleeding from my head."
The 22 people on the ride were safely evacuated around 8:30 p.m. after being stuck for nearly three hours. Two of the riders were "transported to a local hospital for precautionary measures," Magic Mountain spokeswoman Sue Carpenter said.
Magic Mountain visitor Brandy Chambers was on a nearby ride when she saw the accident, she told KTLA-TV Channel 5.
"We were riding on the Jet Stream when we saw the Ninja go into the trees," Chambers said. "It was a lot of leaf noise and then cracking noises … and a lot of screaming."
A specialized urban search-and-rescue team was called in to assist evacuating the riders, who were suspended about 40 feet above the ground. Stranded passengers could be seen talking to firefighters who were working to free them.
The Ninja will remain closed while inspectors survey the track and the area, Carpenter said.
"The safety of our guests and employees is our No. 1 priority," she said.
Thrill seekers, meanwhile, appeared unfazed.
David Walker, 28, from Hollywood, said he and his friends were going to ride the Ninja but decided on another ride about 20 minutes before the derailment.
He said that a couple of rides were shut down around the Ninja, but that most people did not seem unsettled by what happened.
"I wasn't freaked out," Walker said.