Photo/Illutration Toyota Motor Corp. head office in Toyota, Aichi Prefecture (Asahi Shimbun file photo)

Toyota Motor Corp. is among companies that recently discovered improper in-house practices over vehicle and component certification, sources said.

The transport ministry and the companies concerned will make an announcement shortly, the sources added.

Last year, irregularities were found at Daihatsu Motor Co. and Toyota Industries Corp. in applications for type approval, a certificate required for volume production of vehicles and components. Toyota Industries is an engine manufacturer.

The ministry instructed other automakers and related companies to investigate whether similar problems had occurred over the past 10 years.

Toyota and other companies identified improper practices during the investigations and reported them to the transport ministry, the sources said.

The ministry plans to inspect their factories if necessary and may issue administrative punishment, depending on the results, the sources said.

The ministry has served administrative punishment against Daihatsu and Toyota Industries based on the Road Transport Vehicle Law.

In 2022, truck maker Hino Motors Ltd. was also found to have falsified engine emissions and fuel economy performances over type approval.

The transport ministry set up a panel of experts in April to discuss measures to prevent a recurrence.

The panel is expected to compile measures to deter misconduct and detect inappropriate acts early by summer.