Police sent papers to prosecutors earlier this year on a Korean resident of Japan believed to be a North Korean agent for alleged fraud, investigative sources have said.

Investigative authorities believe the 65-year-old man, a resident of Saitama Prefecture, could be a key figure in North Korean espionage activities in Japan.

After analyzing seized documents and the man’s cellphone records, police found he had ties to a Japanese sushi chef who had worked for North Korean leader Kim Jong Un’s late father for more than a decade, the sources said Wednesday.

In his book, the Japanese chef, who goes by the name Kenji Fujimoto, has described a man believed to be him as bringing a message from Kim in 2012 calling for him to visit North Korea again.

Fujimoto served as a special chef for then-North Korean leader Kim Jong Il from 1989 until he left Pyongyang in 2001.

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The chef befriended Kim Jong Un during his stint in North Korea. The elder Kim died of a heart attack in December 2011 at age 69.

Fujimoto went to Pyongyang again in July 2012 at the invitation of the current leader. He has visited several times since, before opening a restaurant in Pyongyang in January last year.

The man allegedly asked a Japanese acquaintance to purchase a large amount of cosmetics at a duty-free store at Narita airport by using a credit card belonging to a different Japanese person in November 2016 and swindled them, according to the sources. Papers on him were sent to prosecutors in June this year.

The man is also believed to have exported products such as cosmetics purchased at the airport to North Korea by way of places such as Beijing, the sources said. Japan bans exports to North Korea under sanctions imposed in the wake of Pyongyang’s nuclear tests.

Investigators are trying to identify the extent of the man’s alleged wrongdoing with Japanese customs authorities. Police in the prefecture are currently looking into the case as a possible violation of the country’s foreign exchange and foreign trade act, the sources said.

For years, Japan has been urging North Korea to resolve the issue of Japanese nationals abducted by Pyongyang in the 1970s and 1980s. In recent months, Prime Minister Shinzo Abe has expressed his willingness to meet with Kim to make a breakthrough.

Tokyo’s stance is that the normalization of bilateral ties will not come unless the abduction, nuclear and missile issues are resolved.