Scholars and residents of Shinjuku Ward, Tokyo, submitted a petition Wednesday to the central government to have a superimposing method used to confirm whether human bones dug up there belong to six wartime prisoners who may have been subject to atrocities committed by the Imperial Japanese Army’s infamous Unit 731.

Dozens of bones were unearthed in 1989 at a site in the ward where the army operated a medical school and epidemic-prevention institute from the 1920s through 1945.

The Group to Investigate the Bone Issues suspects that remains are of victims of wartime experiments carried out by Unit 731, which specialized in biological warfare. It has been calling on the government to make better efforts to identify the deceased as part of its responsibility for owning up to Japan’s wartime misdeeds.

On Wednesday, the group handed documents to Health, Labor and Welfare Ministry officials that include photographs of five Chinese and one Korean who were arrested by Japanese military police and handed over to the unit.

The request for the identification method was written by Wang Yibing, a Chinese who runs a photo studio in Shenyang, Liaoning Province. He offered a photo of his father and cousin. According to the group, both men were held by the military police in 1943 and sent to the army unit in Harbin, Heilongjiang Province, because they were allegedly involved in anti-Japanese activities.

The photographs of the others were copied from books on official documents of the Japanese military police, said Kazuyuki Kawamura, a member of the group. The original documents are being kept in public libraries in China.

“We demanded that the ministry officials consider using the superimposing method,” Kawamura said. The method would impose three-dimensional images of the skulls onto photos to identify the dead. “We are going to ask other relatives of the victims of Unit 731 to provide photographs.”

The government and Shinjuku Ward conducted separate investigations into the bones through scientific tests and interviews and questionnaires with 368 former officers linked to the medical school.

In 1992, the ward said that its results showed the bones were those of at least 62 people, most of whom were Mongoloid. In 2001, the health ministry said it found no solid evidence to link the remains with the activities of Unit 731.