The roller coaster derailment that killed one woman and injured 19 others at an amusement park outside Osaka over the weekend was likely caused by metal fatigue, police sources said Monday.
The broken ends of the axle that failed in Saturday's accident were almost flat, which metallurgical experts say is typical of a metal fatigue fracture, the sources said.
Officials at Expoland park in Suita said the axle had been in use since the roller coaster debuted in March 1992, and the firm was not aware of the part's life span.
The second car of the six-car Fujin Raijin II standup roller coaster derailed and slammed into a 1.1-meter metal guardrail when one of its axles suddenly snapped, the sources said. The 40-cm-long axle is 5 cm in diameter.
Expoland, some 10 km north of central Osaka, was crowded with holidaymakers Saturday for Children's Day, one of the Golden Week holidays, when the accident occurred at around 12:50 p.m.
Yoshino Kogawara, a 19-year-old company employee from Higashi Omi, Shiga Prefecture, was killed in the accident. Her friend, Sayuri Furukawa, 20, from the town of Toyosato, also in Shiga Prefecture, was seriously injured. Eighteen other people sustained slight injuries.
On Sunday, police searched the offices of the operator of Expoland on suspicion of professional negligence resulting in death and injuries.
Expoland officials said the park usually disassembles roller coasters in January or February to check for cracks in vehicle components by using ultrasonic and magnetic wave devices. This year, however, the regular checkup had been put off until May 15, after the Golden Week holiday season, because of a lack of space needed for the procedure, they said.
In a news conference Sunday, Expoland officials said the axle that broke had been in use since the company began operating the roller coaster in March 1992.
