Authorities say all 24 people on a roller-coaster stuck near the top of a Six Flags America ride in Maryland have been rescued.

Prince George's County Fire officials were called to The Joker's Jinx roller-coaster just before 2:30 p.m. Sunday. No injuries have been reported.

"All 24 patrons on the ground being evaluated by EMS," tweeted Maryland Fire Chief Marc Bashoor.

Firefighters reached the cars by tower bucket and each of them was slowly emptied and riders lowered to the ground.

Assistant Fire Chief Paul Gomez said the riders were stuck sitting upright. It took several hours to get them down.

A Six Flags America spokesman said in a statement that it is not yet clear what caused the ride to stop but that it has a computerized safety system that "performed as it is designed to."

Six Flags' website says the ride goes 96.5 km/h per hour and turns upside down four times.