A roller coaster at Six Flags Magic Mountain in Los Angeles derailed on Monday night that left passengers hanging for nearly three hours with four injured.

According to Six Flags publicist Connie Lujan, the incident occurred after a tree branch inadvertently fell on the roller coaster Ninja's tracks that caused the first car to be derailed.

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One of the clamps connecting the first car to the next had reportedly come off leaving some 22 passengers aboard the Ninja precariously suspended at an angle some 20 feet above the ground.

"We were riding on the Jet Stream when we saw the Ninja go into the trees," said Brandy Chambers, a witness to the incident.

"It was a lot of leaf noise and then cracking noises...and a lot of screaming," she added.

The Los Angeles Fire Department, who was the first on the scene, had received the call for help around 6 p.m., said dispatch supervisor Michael Pitt.

Media footage showed rescue teams making use of ladders and heavy equipment to evacuate the passengers.

Firefighters and park maintenance staff were shown wearing harnesses as they worked together to secure the derailed car. Rescue workers started bringing down the passengers at around 8 p.m.

Six Flags spokesperson Sue Carpenter said that all the passengers were "alert and corresponding with park personnel during the evacuation process."

After nearly three hours, all 22 passengers had been safely and successfully evacuated, ABC 10 News has learned.

Fire officials said one had suffered a knee injury while another had complained of neck pain. Carpenter said the two were brought to a local hospital for treatment. Two others were also hurt but only suffered minor injuries, KTLA reported.

"The safety of our guests and employees is our number one priority and as a precaution, the ride will remain closed until a thorough inspection of the area is complete," said Lujan in a statement.

The Ninja roller coaster rides at speeds of about 55 mph where passengers hang from the track and are swung 90 degrees in both directions.

TagsMagic Mountain, Six Flags, Sue Carpenter, Connie Lujan, roller coaster derails, Los Angeles, Ninja Roller Coaster, accident