MELBOURNE (REUTERS) - Roller-coaster riders at Australia's Dreamworld were left hanging backwards on Thursday (March 22) after the ride abruptly stopped, media reported, less than 18 months after four people died in a ride accident at the same theme park.

Six people were left stranded on the BuzzSaw roller coaster for 15 minutes after it came to a sudden halt, news.com.au reported, at the park on the Gold Coast in the north-eastern Australian state of Queensland.

A photograph on social media showed riders seated facing the sky in carriages halted top-to-tail up a tall metal structure.

Dreamworld and owner Ardent Leisure Group did not immediately respond to requests for comment.

"The BuzzSaw controlled stop sensors were activated today at approximately 1.40pm bringing the ride to an immediate stop," a Dreamworld spokesman told news.com.au

She said that all rides were fitted with sensors that could halt rides for reasons that included weather and customer behaviour.

"They are an essential built-in part of ride safety systems. As per standard operating procedures for controlled stops, the ride will be inspected by engineers and retested before it reopens," she said, according to the report.

Four people died in an accident on the Thunder River Rapids ride at Dreamworld on Oct 25, 2016. Demolition of the ride began earlier this month (March).