North Korea has released two Japanese workers who had been detained for almost a year on suspicion of criminal activity.

The men were charged with drug smuggling and counterfitting while visiting a North Korean border town last March.

Japanese officials said Friday the men were returned by way of China earlier this week, but declined to say why they were released.

Japan's National Public Safety Commission chief Jin Matsubara said the release “can be taken as a positive message” and that it could indicate a policy shift under the new leadership of Kim Jong Un.

Relations between Japan and North Korea have long been strained by Tokyo's claims that Pyongyang had been kidnapping Japanese nationals, mostly in the Cold War era.

Many contend that Pyongyang kidnapped the Japanese citizens in order to force them to teach the Japanese language and culture to North Korean spies.

Former North Korean leader Kim Jong Il, who died last month, admitted that Pyongyang abducted Japanese nationals in the 1970s and 1980s. But he said that the issue had been resolved since it later allowed five abductees to return home.

Rights groups say some of the older abductees were apparently killed so North Korean agents could assume their identities. Some in Japan suspect the North is still hiding survivors and has abducted more people than it admits.