The Do-Dodonpa -- the world's fastest rollercoaster -- in Fujiyoshida, Japan, was ordered shut earlier this month after four people suffered broken bones from the ride, Japanese newspaper The Mainichi reported.
The high-speed coaster reaches what operators call a "super death" speed of 112 miles per hour after just 1.56 seconds from launch, taking riders on the world's biggest loop with a diameter of 130 feet, Fuji-Q's website shows.
Operators of Fuji-Q Highland's Do-Dodonpa Word's Fastest Rollercoaster said as a result of the injuries, they have halted "for the time being" the ride at the amusement park. According to Newsweek, the shutdown will last from Aug. 12 until further notice because of "a safety overhaul."
The Do-Dodonpa was designed and built by S&S-Sansei Technologies, and the amusement park welcomed its first visitors on Dec. 21, 2001. Before Do-Dodonpa, the fastest speed record was made by The Superman: The Escape and Tower of Terror.
An apology has been issued by Sansei Technologies to all the injured riders, saying the cause of the injuries remains unknown.
According to park officials, the incident marks the first time riders sustained injuries since the Do-Dodonpa became operational two decades ago.
The rollercoaster was originally designed to hit speeds from 106 mph to 112 mph in 2017, Vice News said.
Park officials made a thorough inspection of the coaster with Sansei after injuries were reported between May and June this year, The Mainichi said, though nothing unusual was found.
It was only after a man in his 30s was reported to have suffered broken bones after riding the coaster earlier this month that the amusement park decided to close down the ride.
The Mainichi reported the coaster riders fractured their bones, "including in their neck and back, with full recovery requiring between one and three months," Newsweek said.
In an interview, Naoya Miyasato, a Nihon University architecture professor who is an expert in rollercoaster designs, said the injuries could result from rapid acceleration.
The coaster's top acceleration is three times the force of gravity. That is essentially equal to the G-forces that astronauts are subjected to during rocket launch.