Japan's Defense Ministry has said that defense-related information may have leaked from Mitsubishi Electric Corp., which suffered cyberattacks last year.

The ministry is closely investigating any possible impact on national security, it said Monday.

Information on bidding for contracts on research on defense equipment prototypes, including on evaluation criteria and required performances, may have leaked, according to the ministry. The information was classified as that requiring careful handling, lower in confidentiality than "secrets" designated by the ministry.

According to the ministry, Mitsubishi Electric had converted paper documents on the information from the ministry into PDF files and kept them on its internal network although the firm was not allowed to do so.

On Jan. 20, the Japanese machinery maker said it had confirmed that no sensitive information on defense or social infrastructure leaked from the company. But a later investigation found possible leakage, the firm said.

In a statement released on Monday, Mitsubishi Electric said, "We are very sorry for failing to thoroughly manage information."

JIJI Press