TOKYO, July 21 (Xinhua) -- Nearly a hundred Japanese citizens and media representatives have gathered in central Tokyo despite the scorching heat for the 35th anniversary of the discovery of human bones from a Japanese army medical school.

Under a blazing sun, they came to attend the meeting on Saturday organized by the Association Demanding Investigation on Human Bones Discovered from the Site of the Army Medical College.

On July 22, 1989, a large number of human bones were found at a construction site in Shinjuku Ward, Tokyo, where now sits the National Institute of Infectious Diseases.

The site was previously home to a medical school and an epidemic prevention institute operated by the Imperial Japanese Army, and it was believed to have been the headquarters of Unit 731, the notorious Japanese germ warfare army during World War II.

In 1990, the association was established to uncover the truth behind the bones and to return the remains to the families of the deceased.

At Saturday's gathering, the association's current representative, Kazuyuki Kawamura, a former Shinjuku ward councilor, said the recently released investigation records by the Japanese Ministry of Health, Labour, and Welfare showed that the bones found in Shinjuku were "human specimens that had been artificially processed."

Some of the bones were transported from the northern Chinese city of Harbin to the army medical college in Japan in iron barrels and wooden boxes, Kawamura added, citing the ministry's investigation records.

Kawamura also noted that a senior official of the former army medical college had told him that the heads of Chinese soldiers killed in battle were brought back to the medical school to be used as specimens, a statement which aligned with the investigation records.

The association believes that the bones discovered at the former Army Medical College site are linked to Unit 731.

In 2001, the health ministry released an investigation report stating that the bones found at the construction site were indeed specimens, but there were testimonies denying that the bones came from outside Japan, making it impossible to definitively link them to Unit 731.

The bones have since been stored at the National Institute of Infectious Diseases, and their true identity remains a mystery.

Kawamura highlighted discrepancies between the recently disclosed investigation records and the 2001 report, suggesting that the report had been altered. "They were trying to hide the fact that eyewitnesses had directly seen and experienced these events," he said.

Furthermore, Kawamura stated that the Japanese government's refusal to question individuals related to Unit 731 and its deliberate exclusion of the unit from the investigation makes it impossible to uncover the truth.

The association hopes that an independent, impartial, professional, and internationally influential third-party organization will step in to investigate.

Also on Saturday, Hideo Shimizu, a 94-year-old former Unit 731 Youth Corps member, participated in the gathering via video link. He confirmed that he had seen "specimens with heads cut in half in the unit's specimen room," urging the Japanese government to face historical facts.

Japanese citizens attending the meeting expressed their frustration with the health ministry's deliberate avoidance of investigating Unit 731.

Unit 731 represents the dark shadow of Japan's aggressive wars, and it is essential to inform the public of its actions, Tatsuo Kawano, a participant at Saturday's gathering, told Xinhua, adding that he hoped the gathering would lead to new progress in the investigation.

"Telling historical truths to future generations is a crucial step in reflecting on war," said a resident of Shinjuku's Toyama district who goes by the alias of Yamada.