Nidec Shares Tumble After Scandal Spreads to Product Quality

The Nidec Corp. headquarters building in Kyoto, Japan.

Photographer: Fred Mery/Bloomberg

Nidec Corp. shares fell after the company identified more cases of improper conduct, this time involving the quality control of motors and other products.

The issues included changes made to materials, processes and designs without approval, Nidec, the world’s largest manufacturer of precision motors, said in a statement Wednesday. Shares fell as much as 18% in Tokyo.