Police said Wednesday they have arrested two Nigerians on suspicion of smuggling around 4 kg of stimulant drugs from Kenya and later seized illegal drugs with a street value of ¥1.5 billion.

Okafor Stanley Okezie, 39, living in Matsudo, Chiba Prefecture, and Nwozor Mark Chidi, 43, of Tokyo, allegedly conspired to smuggle stimulant drugs from Kenya in October by using Express Mail Service, the police said. An X-ray inspection at Osaka Customs detected the drugs, according to the customs authority.

Around 18 kg of stimulant drugs and about 1.4 kg of cocaine have been seized from places linked to the men, the police said.

While the two men, who were indicted Wednesday for violating the stimulants control law and the customs law, have denied the charges, the police suspect the involvement of an African-based trafficking organization, they added.