The police have also detected a surface imprint on the neck of Miyako Hiraoka, who is from Hamada, Shimane Prefecture, and a first-year student at the University of Shimane, prompting them to believe she may have been strangled and her head cut off with a knife, investigative sources said.

The joint investigation squad of the Shimane and Hiroshima prefectural police is investigating the cause of her death through an autopsy, while seeking other parts of her body, they said.

The squad is questioning local people as to whether they saw a suspicious vehicle on National Route 186, which connects Hiroshima and Hamada, as it believes her body parts were carried in a vehicle after her death because no bloodstains have been found near the site.

The investigators are also asking Hiraoka's friends whether she had been involved in any trouble.

An autopsy conducted on her head has found that Hiraoka was killed within five days of going missing after finishing her part-time job on the evening of Oct. 26, and has confirmed signs of blows to the face. But it failed to specify the cause of her death.