A police spokesperson said the bomb was recovered from one of the coaches of the Kamakhya-Puri Express near the Pancharatna station in western Goalpara district early today.
The train was bound for Puri in Orissa from Assam's main city of Guwahati.
Goalpara district police chief Luis Aind said, "We had some information that a bomb was being carried in the train and hence we conducted a massive search operation after stopping the train at Pancharatna station and recovered a powerful improvised explosive device concealed in a sack."
Bomb experts defused the explosive.
Police picked up one person suspected to have been carrying the bomb.
The official said, "Investigations are on to find if the person we picked was actually carrying the bomb or not."
On July 11, at least 70 people were injured, several of them seriously, when four coaches of the Kamakhya-Puri Express were derailed and four others capsized due to a powerful explosion at Dhatkuchi between Rangiya and Goghrapar railway stations in Assam in western Assam.
Militants in Assam have stepped up efforts to create terror ahead of Independence Day even as 12 rebel groups have called for a boycott and a 17-hour general strike Aug 15.
Militant groups in the northeast have for years boycotted national events to protest New Delhi's rule over the region.
Security forces have been put on maximum alert across the region to thwart possible rebel strikes, officials said.
The run-up to the events has always been violent, with rebels striking vital installations like crude oil pipelines, trains, roads and rail bridges besides targeting security personnel.
