North Korea failed to include information about Japanese abductees in a report it presented to Japan during negotiations in the spring, sources familiar with the matter said on Tuesday.

Japan rejected the report, in the absence of information about 12 Japanese whom it recognizes as abduction victims who are still missing, an issue on which Tokyo has placed a high priority, the sources said.

North Korea told Japan that it “is investigating” the abduction cases, they said.

The report contains North Korea’s findings of the remains of Japanese who died around the 1945 end of World War II in what is now North Korea and the Japanese wives of pro-Pyongyang Korean residents of Japan who moved to North Korea under a 1959-1984 resettlement project.

The Korean Peninsula was under Japanese colonial rule from 1910 to 1945.

During the negotiations, North Korea demanded that Japan lift more sanctions in return for information about the remains and the Japanese wives based on the principle of reciprocity, according to the sources.

Pyongyang also demanded that Tokyo provide funds for collecting the remains because it would be costly to retrieve them.

Japan said North Korea must present its findings on the abduction victims by July, a year after Tokyo lifted some of its sanctions on North Korea in return for the launch of a new investigation into the abduction victims, as well as a comprehensive probe into all Japanese nationals residing in North Korea.

While Japan regards the deadline as July, some in the government say Tokyo should wait until September to determine whether to reinstate sanctions on North Korea because Pyongyang said last September that it would carry out the investigation in about a year.

Since January, Japan and North Korea have held unofficial monthly talks in China, according to the sources.

Junichi Ihara, director general of the Asian and Oceanian Affairs Bureau of the Foreign Ministry, is believed to have met with officials of the Ministry of State Security, North Korea’s secret police organ, and Song Il Ho, Pyongyang’s ambassador for negotiations to normalize relations with Japan.

Japan attaches the highest priority to North Korea’s reinvestigation into the fates of the abduction victims, or those abducted in the 1970s and 1980s presumably to train spies in Japanese language and culture.

Japan officially lists 17 nationals as abduction victims but suspects North Korea’s involvement in many more disappearances. While five of the 17 were repatriated in 2002, Pyongyang has maintained that eight have died and four others never entered the country.

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

The abduction issue has prevented Tokyo and Pyongyang from normalizing diplomatic relations.