SEATTLE (REUTERS) - Twenty-four people were rescued on Sunday from a Maryland roller coaster that malfunctioned, leaving a car stuck for hours near a high point of the ride, emergency officials said.

The passengers were trapped about 75 feet (23 metres) in the air atop the Joker's Jinx roller coaster at the Six Flags America amusement park in Upper Marlboro, outside Washington, fire officials said.

The ride stopped working at 2.30pm local time and the rescue took about four hours, according to Prince George's County Fire Chief Marc Bashoor.

Crews used a tower bucket to reach stranded passengers. They were unstrapped one by one, loaded into the bucket and then lowered to the ground, he said. The passengers were checked by medical personnel before being released.

Six Flags Entertainment Corp said in a statement that the ride would remain closed during an investigation into what caused the malfunction.

"While we are not yet sure what caused the stoppage, the ride performed as it is designed to," Six Flags said in a statement.