The Defense Ministry has said that defense-related information may have leaked following cyberattacks on Mitsubishi Electric Corp. last year.

The ministry is closely investigating whether it will have an impact on national security, it said Monday.

Information pertaining to bidding for contracts on defense equipment research, including evaluation criteria and required performances, may have leaked, according to the ministry. The information was classified so as to require it to be handled carefully, albeit at a lower level of confidentiality than “secrets” designated by the ministry.

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

On Jan. 20, the 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 leaks, the firm said.

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