They said the boy's father took him to a barber's shop yesterday and then went for work, but found him missing when he returned.
Meanwhile workers of a local sago factory reported that a body has been found in the effluent tank and when it was fished out, it was confirmed to be the boy.
Police said a case has been registered under Section 174 of Crpc (police to inquire and report on suicide). They said the deceased was mentally ill and his parents used to tie his hands and legs to prevent him from going out.