However, Mitsubishi Material has informed that no safety or legal issues have been raised in both the cases.
A copper production unit of Mitsubishi Materials, Mitsubishi Shindoh Co., was also found to have falsified inspection data on products including brass strips used for components in the automotive industry.
Mitsubishi Materials expects the results of its investigation to be released by the end of the year. The subsidiaries were also found to have used false data on copper products which have been shipped to 29 companies.
The company, which submitted a report to the government Friday, said three of its subsidiaries faked data on products to meet specifications.
Japan's Transport Minister Keiichi Ishii said the latest scandal to rock Japan's manufacturing industry was highly regrettable and after reviewing the report ministry-led probes would be conducted to ensure product safety.
That joint venture includes the Hatano plant that has become the focus of Kobe Steel's data falsification scandal, and been stripped of numerous Japanese and global quality certifications.
Mitsubishi Shindoh started an internal probe last month and discovered the data falsification. He added that he considers it a matter for the companies and not an industry-wide issue.
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Mitsubishi Shindoh Co. said its products with falsified inspection data were sent to 29 firms between October 2016 and October this year.
Officials at the Acquisition, Technology and Logistics Agency, under the auspices of Japan's Defense Ministry, said products including rubber seals installed in components related to hydraulic systems used on Japanese Self-Defense Forces' aircraft and ship engines, did not meet the requested specifications.
Local media cited the economy minister, Hiroshige Seko, telling reporters Friday he was asking Mitsubishi Materials why it waited more than six months to report the problem after it was discovered.
Kobe Steel's crisis erupted in early October, collapsing its shares. That has allowed its stock to recover some of its losses.
Kobe blamed lax controls and too much focus on profit for its shortcomings, including unrealistically high standards that exceeded clients' expectations and encouraged staff to disregard quality guidelines for a decade or more. Three of its units were found to have falsified data for products supplied to almost 300 companies in the aerospace, vehicle and electric power industries, the company said.
"Even if Mitsubishi Shindoh and Mitsubishi Cable don't make up a big portion of the company's earnings, not just the short-term impact but the mid- and long-term impact on its orders is a cause of concern", Keiju Kurosaka, senior analyst at Mitsubishi UFJ Morgan Stanley Securities, said in a note.
The company's share price plunged 11 percent, ending the day down more than 8 percent Friday.