A high-level central team will visit Assam on Friday to assist in the investigation into the explosion in Rajdhani Express in the wee hours.
Home Minister Shivraj Patil has strongly condemned the blasts in which five passengers were killed, an MHA spokesman said.
The Home Ministry is closely monitoring the situation.
Home Secretary Madhukar Gupta has spoken to the state chief secretary to take stock of the situation.
At least five passengers were killed when suspected tribal insurgents exploded a powerful bomb in the Delhi-bound Rajdhani Express killing five passengers and injuring nine in upper Assam's Golaghat district.