Police arrested four people on Thursday for allegedly abandoning the body of a 6-year-old boy in the city of Kobe.
The four in custody include the boy's mother, Saki Hosaka, 34, his uncle, Daichi, 32, and his aunts, Tomomi and Asaka, both 30.
The boy, Nao, is believed to have died of traumatic shock. An iron pipe was among the items confiscated from an apartment in Kobe where the four and the boy lived.
The Hyogo Prefectural Police believes that the boy was abused, informed sources said.
The four relatives are suspected of dumping Nao's body in a suitcase in a grassy area about 800 meters from their home around June 19. The suitcase is believed to have been brought by the uncle, Daichi, when he moved in the apartment around the end of last year.
On June 22, they were arrested for allegedly holding the boy's grandmother captive in the apartment and injuring her by beating her with a stick-like object. Nao's body was found the same day.
An autopsy found that the boy likely died around June 19. On that day, local residents saw the four carrying a suitcase around the evening, and security cameras also captured the scene.