A couple and their 13-year old son have been missing since yesterday from Lower Majuli's Borduwa Chapori in the world's largest river island, police said today.
The police suspect the family was killed following the death of a youth in March after which the local people had alleged it was due to witchcraft practised by the family.
The authorities had carried out awareness programmes following the incident.
The missing members are Rajkumar and Bornali Doley along with their son Moni Doley.
Police investigation was on.