SHIZUOKA (Kyodo) Yamaha Motor Co. helped the trade ministry in 2005 formulate stricter export controls on unmanned helicopters, investigative sources said Saturday.

Three Yamaha Motor employees were arrested Friday for allegedly attempting to violate the controls by shipping a remote-controlled helicopter to China.

The police intend to investigate the company's in-house export procedures, suspecting the arrested employees had full knowledge of the rules, including which models are banned for shipment abroad and those that require export authorization to prevent their military or terrorist use, the sources said.