Vaishnaw said that the actual reason behind the accident could be ascertained only after dismantling the engine's equipment.
Twelve coaches of the Bikaner-Guwahati Express train had derailed and some of them capsized near Domohani in Jalpaiguri district on Thursday.
"Since some of them are in a critical condition, the death toll may go up," Jalpaiguri DM Moumita Godara Basu said, adding rescuers thoroughly searched each coach for survivors and bodies through darkness and thick fog.