Japanese authorities have arrested seven Chinese men on suspicion of smuggling what was believed to be a record amount of stimulants by ship-to-ship transfers.

Tokyo police said Wednesday seven Chinese men aged 24-40 were arrested this week on suspicion of illegally possessing "large amounts" of stimulants on the Izu coast, west of Tokyo.

NHK television said 35-year-old suspect Lin Jingsheng and six other men allegedly smuggled nearly 1 ton of amphetamines, a record one-time seizure in Japan made Monday estimated to be worth 60 billion yen ($550 million). Police earlier found an unattended boat carrying drug-filled bags on the beach.

The arrests were part of an ongoing investigation into an international drug ring following reports of suspicious ships spotted in the area.