Two people were injured today at an amusement park in central Japan when the world's tallest and longest roller coaster came to a halt after dropping a wheel.

The 'Steel Dragon 2000,' which zooms along a 2,479m track and drops 93.5m, lost one of the right wheels off the front coach during its 18th run of the day at the Nagashima Superland park outside Nagoya, 300 kilometers west of Tokyo.

A 20-year-old woman, one of the 34 passengers aboard, was sitting in the third coach of the six-coach coaster and banged her back against her seat.

A 28-year-old man swimming in a nearby pool was hit in the hip with the 32cm wheel. Both were taken to hospital for treatment.

The other passengers disembarked from the ride without incident.

'We are trying to determine if the accident resulted from any negligence,' the police official said.

'The accident occured on the day's 18th run. If it happened on the first run, inadequate checks could have been possible.'