Bodies of Prem Yadav (55), his wife Radhika (50), daughter Monika (18) and son Kanhaiya (13) were found on the railway tracks while another son Shivam (14) was found in a serious condition, police said.
The bodies have been sent for post mortem while the injured has been referred to Varanasi hospital, they said.
The locals have expressed doubts that the incident could be a fall out of some property dispute, police said, adding that it would be known only after the post mortem examination if they were run over by the train or killed and put on the tracks.