Tokyo ? Government officials laid flowers at a tomb Wednesday then sealed it on hundreds of human bone fragments, hoping to bury the debate on World War II human experiments by the Imperial Army.

Some researchers believe the shattered skulls and thigh bones are the remains of nearly 100 prisoners of war who died in germ warfare experiments conducted by the Imperial Army’s shadowy Unit 731 in northern China.

While the exact origins of bones remain a mystery, the Health Ministry maintained it was only appropriate to give them a final and proper burial after more than 10 years collecting dust in a Tokyo storehouse.

The bone fragments, some of which bore knife marks, bullet holes and drilling abrasions, immediately drew suspicion after they were unearthed in 1989 at the site of the wartime army’s medical school.

The school was believed to have controlled the notorious Unit 731, based in Harbin, China, which historians and former unit members say injected prisoners of war with typhus, cholera and other diseases for biological war research.

Citing Unit 731’s close cooperation with the school, Keiichi Tsuneishi, a history professor at Kanagawa University, was among the first to say it was likely the bones were remnants of bodies shipped from China after the experiments.

Hajime Sakura, an anthropologist who briefly studied the bones shortly after they were discovered, said they were not conclusively linked to germ experimentation but displayed characteristics of experimental surgery at the least.