Three Chinese men were arrested Sunday on suspicion of attempting to pick up four bags containing a combined 120 kg of an illegal stimulant with an estimated street value of 12 billion yen in a fishing port in Kochi Prefecture, police said.

In addition, a local Japan Coast Guard office said it had apprehended six Chinese crew members of a fishing boat for not obeying a Coast Guard order to stop in nearby waters. The police suspect the boat may have transported the stimulants.

The four bags were found Saturday in the port in Muroto after a Japan Coast Guard airplane had spotted the suspicious boat off Cape Muroto earlier in the day, according to the prefectural police and a regional Coast Guard office.

They said the plane spotted the boat about 90 km southeast of the cape at around 4 p.m. Saturday and informed the Kochi Coast Guard office, which then notified the Kochi prefectural police at about 9:30 p.m.

About an hour later, police officers who were patrolling the port area found the bags, each of which contained about 30 kg of white powder, on a dike at the port.

A police test on one of the bags confirmed it contained a stimulant and they believe the other three contain the same substance.

The police also received a report that several men had left the port by car around the same time.

Two men in the car were later located in neighboring Tokushima Prefecture and a third man was apprehended near the site where the bags were discovered, leading the police to arrest the three — all Chinese in their 30s — on suspicion of violating the drug control law.

The boat's 47-year-old captain and five crew members were apprehended for seeking to avoid a Coast Guard inspection in violation of the fisheries law.