About 20 people were trapped on a roller coaster for several hours outside Baltimore, Prince George’s County fire officials said.

Officials say it happened on the roller coaster called “Joker’s Jinx” Firefighters had to take each individual down using a harness.

Mark Brady, the Prince George County Fire Department spokesman, posted on Twitter that their plan was to “remove children first.”

Just after 7 p.m., the first adult and two children had been lowered. By 9:30 p.m., all the riders had been rescued and just the firefighters needed to come down.

Six Flags issued a statement saying the roller coaster stopped “at a safe site,” but did not list the reason by the ride could not complete its regular ride cycle.

On its website, Six Flags describes the “Joker’s Jinx” ride’s top speed is 60 mph and was introduced to the park in 1999.