Do-Dodonpa in Japan’s Fuji-Q Highland Park has been closed until further notice after at least six riders were injured. Four of them broke their back or neck, likely caused by the ride’s extreme speed which reaches 110mph in under two seconds.

       The ride was the fastest-accelerating coaster in the world and reaches a G-force comparable to a rocket launch.

       Sansei Technologies, who designed the ride in 2001, say there had been no reports of broken bones until December last year and do not know what caused the injuries.

       Fuji-Q Highland also say no technical issues were found during an investigation.

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       Naoya Miyasato, an architecture professor from Nihon University, told Vice News: “Rollercoaster designs must all abide by government-approved standards, so the fact that there are multiple similar accidents is unusual.”

       Mr Miyasato said that the most likely cause of injury is the ride’s rapid acceleration and the way riders sit.

       He continued: “If a rider can’t withstand the acceleration, then they sustain injury, which could be what is happening here.

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       “If they detected no serious concerns with the actual ride, then it could be the way people were sitting. But if a person was sitting incorrectly, say with space between their backs and their seat, it is the responsibility of the park employees to check their seating position.”

       The Do-Dodonpa requires riders to lean back against their seat and keep as little space as possible between their back and the backrest .

       However, according to Japanese news outlet Mainichi Shimbun, one of the riders who reported an injury said she may have been sitting forward during the ride.