The roller coaster that derailed at the Expoland amusement park outside Osaka last Saturday, leaving one woman dead and 19 others injured, had passed all annual maintenance checks since 2004 with flying colors, police and local administrative sources said Thursday.
Previously, Expoland admitted giving top ratings to every item on the inspection checklist in spite of neglecting to carry out the annual check in January.
A senior Expoland official has said that he did not know an annual inspection was required, while another official in charge of checks has said the park skipped it only this year.
Police, suspicious of the claims, will try to put together a realistic picture of maintenance procedures at Expoland, the sources said.
The amusement park, located at the site of the 1970 Exposition in Suita, Osaka Prefecture, was crowded with holidaymakers last Saturday, Children's Day, when the accident occurred at around 12:50 p.m.
The second car of the six-car standup roller coaster derailed and hit a 1.1-meter-high steel guardrail. Yoshino Kogawara, 19, who was in the second car, was killed.
Amusement park operators are required to submit the results of annual checks of their equipment to local governments. The results of Expoland's checks since 2004 are on file with the Suita Municipal Government, the sources said.
The checklist covers 47-56 items, including car platforms and wheel units. The axle of the roller coaster car that derailed had received A ratings. However, investigations have shown that metal fatigue was the likely cause of the axle break that led to the derailment.
Metallurgists say Expoland would have detected signs of weakness in the axle if proper annual checks had been carried out, noting it takes several years for cracks due to metal fatigue to rupture.