NHK has learned that Kobe Steel submitted to the Tokyo District Prosecutors Office documents related to the firm's falsified product inspection data.

Sources familiar with the matter say the submission was made at the prosecutors' request to the Japanese steelmaker.

The prosecutors and the Tokyo metropolitan police are likely to investigate the firm on suspicion of violating the Unfair Competition Prevention Law.

The data falsification first came to light last October. Kobe Steel has since said it shipped aluminum, copper, steel and other products with altered data.

Last month, the company released the final report of an external panel that says falsely certified products were shipped to 688 companies and that 5 current and former executives were involved.

Kobe Steel chairman and president Hiroya Kawasaki resigned from the posts on April 1st.

It's now known that falsely certified products were shipped to companies including aircraft and vehicle makers outside Japan.

The US Justice Department has already asked Kobe Steel for documents. Consumers in the US and Canada have begun procedures for damages lawsuits.