TOKYO - Japan's antitrust watchdog plans to issue a warning to a Toyota Motor Corp subsidiary after discovering it forced subcontractors to store auto parts molds without paying the costs, local media reported Sunday.

Toyota Customizing & Development Co, which makes auto parts, ambulances and racing cars, allegedly forced about 50 suppliers to retain more than 650 molds and inspection instruments for parts used in its past vehicles, even though it did not plan to place new orders, Kyodo News said, citing a source familiar with the matter.

The subsidiary, in which Toyota holds a 90.5-percent stake, has admitted to violating the subcontract law, the report said.

The Japan Fair Trade Commission also suspects that the Toyota group company returned over 50 million yen (about $310,000) worth of parts to more than 60 suppliers without valid reasons.

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The commission plans to warn the subsidiary to take measures to prevent a recurrence, the report said.