Two Taiwanese men have been arrested for allegedly attempting to smuggle 4 kg of stimulant drugs into Japan, law enforcement authorities said Thursday.

According to Narita airport police, 43-year-old Ni Yuan-lei and Chen Fen-hsu, 32, both company employees from Taiwan, arrived at Narita airport on separate flights from Hong Kong on the evening of March 17.

The smugglers each had 20 100-gram plastic sachets of amphetamines sewn into their vests, the police said, adding that the haul has an estimated street value of 240 million yen.

Although Ni and Chen have told the police they do not know each other, police and customs officials believe the two could belong to the same smuggling organization.

Customs officials at New Tokyo International Airport in Narita said they were alarmed by the increasing number of Taiwanese passport holders trying to bring in drugs on flights via Hong Kong in 2000.