( CNN ) -- Rescuers pulled stranded riders from a roller coaster at Six Flags America in Maryland on Sunday after the ride halted on the tracks . A train on the Joker 's Jinx roller coaster stopped near the top of the 79-foot-tall ride , fire officials said . It took more than four hours to get all 24 passengers back on the ground . No one was injured , Six Flags spokeswoman Debbie Evans said . Video from CNN affiliate WJLA showed rescuers slowly helping passengers to safety , one by one . Hours after the rescue operation began , Prince George 's County Fire Chief Marc Bashoor said all passengers were safe . He posted a series of photos of the dramatic rescue on Twitter . `` Firefighters have reached the 1st car by tower bucket - each of 6 cars will be emptied slowly , '' he wrote . `` Riders being strapped in place within each car , before cars passenger restraint can be released , '' he said minutes later . `` Then pulled 1 by 1 - 1st 2 people in bucket . '' Volunteer firefighters tweeted a photo showing two aerial towers they were using to help passengers to safety . Officials do n't know what caused the coaster to halt , Evans said . `` The ride has a sophisticated , computerized safety system that can cause such ride stoppages . While we are not yet sure what caused the stoppage , the ride performed as it is designed to , '' she said . On its website , Six Flags America says the ride normally lasts for just over a minute and reaches a speed of 60 mph . `` Without any pauses or braking , you 'll blast through a cobra roll , a sidewinder loop , a corkscrew , and countless swift reversals in between , '' the website says . When the ride blasts to 60 mph in just over three seconds , the description says , `` that 'll wipe that smirk off your face , as you are shot like a bullet into four inversions compressed into a half-mile pile of twisted steel . '' Evans said Sunday that the Joker 's Jinx would be shut down while officials determine what happened . `` The ride will remain closed until the park completes a thorough investigation and both the staff and ride manufacturer have determined the ride is safe for operation , '' she said . `` The safety of our guests is our top priority . '' Six Flags roller coaster car derails , 4 injured . Disney World monorail evacuated after power outage .
NEW : All 24 passengers are safely on the ground , fire chief says . The Joker 's Jinx roller coaster stops on the tracks at Six Flags America . Comment: No one is injured , all riders `` are secure '' The ride will closed while officials investigate , she says .