TOKYO (Kyodo) -- Three Japanese company executives were arrested Wednesday on suspicion of illegally exporting equipment capable of producing biological weapons to China more than three years ago, without obtaining prior approval from trade authorities, police said.

The three are 70-year-old Masaaki Okawara, the president of Yokohama-based machinery maker Ohkawa Kakohki Co., Shizuo Aishima, 71, the company's adviser, and Junji Shimada, 66, one of its directors, the police said.

They are suspected of having exported a spray dryer on June 2, 2016, knowing that its overseas shipment was restricted under Japanese law, according to the police.

They are believed to have falsified the dryer's functions to avoid the restrictions, although the shipment had to be authorized by the Ministry of Economy, Trade and Industry.

The Tokyo police's Public Security Bureau has searched Ohkawa Kakohki, Japan's largest maker of spray dryers, and analyzed confiscated documents to narrow down the final destination of the exported device and its use.

Spray dryers, used to produce medical and food products, can atomize liquids into mists and then turn them into powder. The company, founded in 1980, has exported its devices to Asia, Europe and the United States, according to its website.

The bureau said it sold and shipped the equipment to a German chemical firm's unit in Shanghai for 18 million yen ($172,000). The unit is said to have used the device to produce materials for lithium-ion batteries.

Besides the 2016 shipment, the bureau believes there are other similar cases involving Ohkawa Kakohki.

A spokesperson for the company said, "We cannot comment at this stage."