Japan's largest cargo-rail operator says it is working on internal reforms to prevent data tampering.

Japan Freight Railway disclosed last month that data on wheel-to-axle fittings had been fabricated for at least a decade.

Company President Inukai Shin said, "We will focus on proper countermeasures and responses first, and then look into what action to take against management and others involved."

He said reference figures for train car maintenance had varied from one office to another. They have since been standardized. He also said an internal audit team will be set up.

The firm says the data manipulation affected more than 600 cars. Inukai said the company is going to confirm their safety and resume their operation at the end of the year.

The company's reforms are scheduled to be completed by January.