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A popular roller coaster at Six Flags Magic Mountain that derailed and got stuck, leaving nearly two dozen riders suspended in the air for hours, struck a large pine tree that fell on the tracks, according to a spokesman for the state safety agency that had investigators at the park Tuesday.

Rescuers worked to help passengers off the Ninja roller coaster at Magic Mountain July 7, 2014. (Credit: KTLA)
Rescuers worked to help passengers off the Ninja roller coaster at Magic Mountain July 7, 2014. (Credit: KTLA)

The Ninja ride — a swinging, suspended roller coaster from which 22 people were rescued Monday night — was set to remain closed until investigators determined it was safe, Cal/OSHA spokesman Peter Melton said.

The rest of the Santa Clarita park was open Tuesday.

Ninja had “a clean bill of health,” as far as the Division of Occupational Safety and Health was concerned, Melton said. The division inspects theme park rides annually, Melton said, but he was not certain when the most recent inspection of the Ninja took place.

Before Monday, the only record of a problem on the Ninja occurred more than five year earlier when a guest tried to retrieve a hat, jumped a fence and got hit by the roller coaster, Melton said.

“Other than that, the Ninja has been fine since it was built in 1988,” he said.

Investigators were in the process of getting records that would help in the case, Melton said.

On Monday, Los Angeles County firefighters were called to Magic Mountain about 6 p.m. with a report of multiple injuries and passengers suspended in air on the roller coaster.

A tree branch had fallen on the tracks, “obstructing the train,” a park spokeswoman said Monday night.

A car on the ride came around a bend and hit what appeared to be a pine tree that fell across the tracks, causing the car to derail, county Fire Department inspector Rick Flores said.

Melton said the pine tree was between 30 and 40 feet tall. A certified arborist was called in Tuesday to check the tree, and it remained unclear why it fell, Melton said.

The 22 riders were alert during the evacuation, Magic Mountain spokeswoman Sue Carpenter said.

Firefighters worked for several hours to free riders, four of whom were injured. Two of those with injuries were taken to a local hospital for “precautionary measures,” Carpenter said.

Those injured were in the first car, Flores said.

A YouTube video that was posted last year, taken from the point of view of the first car, shows that riders pass under trees, over water and above other parts of the park.