Pyongyang briefed Tokyo on its questioning of people suspected of involvement in the abductions of Japanese nationals when the two sides held an informal meeting in late January in Shanghai, according to a Japan-North Korea diplomatic source.

The move was apparently aimed at demonstrating North Korea’s latest efforts to investigate the abductions of Japanese in the 1970s and 1980s, hoping Tokyo would further ease its economic sanctions on the country.

It appears, however, that the results of the latest questioning failed to bring about any progress on the issue of the Japanese abductees, the source said on Sunday.

North Korea had proposed questioning those suspected of involvement in the abductions as an initial stage of its investigation when the two countries held formal governmental talks in October in Pyongyang.

According to the source, North Korea is believed to have told the Japanese side at the January meeting that it questioned several people, including Japanese hijacker Kimihiro Uomoto, whose former surname was Abe, and the Japanese wives of two other men involved in the 1970 hijack of a Japan Airlines airplane.

Uomoto, who defected to North Korea after the hijacking, and the two women have repeatedly denied their involvement in the abductions of Japanese nationals and did so again in the latest questioning, the source said.

It is unclear whether Pyongyang’s latest questioning attempt included Sin Kwang Su and Kim Se Ho — two North Korean agents who are believed to have abducted Japanese, according to the source.

The National Police Agency suspects Uomoto was involved in the abduction of Keiko Arimoto, while the two wives of the hijackers were linked with the abduction of Kaoru Matsuki and Toru Ishioka.

Arimoto, Matsuki and Ishioka are among 17 nationals Japan officially lists as abduction victims.

Five of the 17 were repatriated in 2002, but North Korea has maintained that eight have died and four others never entered the country.

The informal talks in Shanghai were attended by Junichi Ihara, director-general of the Asian and Oceanian Affairs Bureau of the Foreign Ministry, and senior officials of the Ministry of State Security, North Korea’s secret police agency directly linked to the nation’s leader, Kim Jong Un.

Japan has continued to put pressure on North Korea after Pyongyang failed to honor an agreement the two countries reached last July that the first report on the abduction probe would be released sometime between late summer and early fall 2014.

North Korea conducted investigations in 2002 and 2004 into its abductions of Japanese nationals, but Japan rejected the results as unconvincing.