Tokyo ? The National Police Agency said at an international conference last week it suspected that North Korea was operating three factories producing stimulant drugs, it has been learned.

Hiroto Yoshimura, deputy commissioner general of the NPA, made the claim during a speech as a Japanese representative at the U.N. Commission on Narcotic Drugs’ closed-door meeting in Vienna on Wednesday.

The commission is under the U.N. Office on Drugs and Crime.

Two of the three factories are located in areas where pharmaceutical factories were situated when the Korean Peninsula was under Japanese colonial control, according to sources.

It is highly possible that North Korea is using these factories to produce the stimulant drugs, they said.

It is the first time the NPA has mentioned at an international conference the possibility of North Korea operating stimulant drug factories.