Braja Dulal Pal (60), his wife Anita Pal (54) and son Rajat Pal (32) of Uttar Pratapgarh village died on the spot, even as the police were yet to ascertain the motive of the three to end their life.
Train services on the up and down line of Sealdah main section were disrupted due to the incident.
Railway sources, however, said the three were knocked down by the speeding train.
Post mortem will be conducted on the bodies, police said.
In another incident an unidentified man aged around 34 years was run over and killed by a train between Sodepur and Agarpara railway station in North 24 Parganas district, police sources said.
