All 24 riders on a stalled roller coaster were brought down safely by Sunday evening after they were stranded high above the ground for hours at the Six Flags America amusement park in Prince George’s County.

There were no indications of serious injuries to any of the riders, including seven children, who had been on the Joker’s Jinx at the park for as long as five hours.

Shortly before 8 p.m., county Fire Chief Marc Bashoor said none of the rescued riders appeared to require hospital treatment.

Firefighters set up a 105-foot tower ladder to reach the track and removed some of the fencing around the ride to access the cars, Bashoor said. They removed people from the ride by bucket, placing safety harnesses on the riders before lowering them one car at a time.

“It was not very hard to keep the victims calm,” said Owen Hardy, one of the firefighters who went up to help the passengers. “There really were no frantic individuals and all seemed to be in good spirits. I think they were just relieved to see us come to their aid.”

Firefighters make face-to-face contact with riders stuck about 75 feet in the air Sunday on the Joker's Jinx roller coaster at Six Flags America in Prince George’s County, Md. (Fire Chief Marc Bashoor/Prince George's County, Md., Fire/EMS)

Police were called to the park about 2:30 p.m. after reports that six four-person cars on the ride had stopped at about 75 feet up, near the top of the ride, said Assistant Fire Chief Paul Gomez. Firefighters climbed onto the ride about 30 feet down the track from the stranded cars and spoke with the riders about 3:50 p.m, he said. First responders began delivering water while determining the safest way to conduct the rescue.

The department had practiced rescues on the Joker’s Jinx, Bashoor said.

The cars on the track are secure and were unlikely to move. Although the cause of the problem was unknown, the ride has a computerized safety system that can trigger such stops, according to a statement from the park.

The ride has been inspected daily since it opened in 1999, Six Flags spokeswoman Debbie Evans said.

Joker’s Jinx carries 24 people at a time and has a 54-inch height requirement.

The section of the park near the ride will remain closed until Six Flags staff and the ride’s manufacturer determine that the ride is safe. The rest of the Six Flags complex remained open Sunday.