A criminal investigation has been launched into Kobe Steel Ltd.'s product data fabrication scandal — one of a series of similar problems that surfaced at major Japanese companies and shook international trust in the nation's manufacturing industry. The joint probe by the special investigation squad of the Tokyo District Public Prosecutor's Office and the Metropolitan Police Department should aim to rebuild that trust by exposing how and why falsification of product inspection data has been allowed to go on for decades. The correct lessons must be learned to prevent a recurrence of the problem.

In the scandal that surfaced last October, inspection data on Kobe Steel's aluminum and copper products at 23 domestic and overseas plants was found to have been altered to make it look like the products met customer specifications, such as strength, when in fact they did not — or sometimes the data was fabricated without inspections taking place. The data falsification reportedly dated back at least to the 1970s at an aluminum product plant in Tochigi Prefecture.

Products with falsified data had been shipped to more than 600 of Kobe Steel's domestic and overseas customers and were used in products ranging from automobiles to passenger jets and bullet trains — whose performance directly affects the safety of consumers. Some of the products were used in nuclear power plants; Kansai Electric Power Co. delayed the restart of its Oi plant in Fukui Prefecture by two months because of the data falsification problem.