State Additional Director General of Police Brij Lal said that the bomb was spotted by a woman passenger who immediately notified the police.
"The bomb was noticed by Kaushla Devi, a middle-aged passenger, as soon as she entered the toilet after embarking at Mahoba station that was the first halt after Chitrakoot from where the train had started,' he said.
Following which the railway authorities got the entire train and platform cleared of passengers and a bomb-disposal squad was summoned from a neighbouring district, he said.
He added that the bomb was diffused by the bomb disposal team, who reached the spot after midnight.
He said that the coach where the bomb was placed was detached from the train and taken to corner at Mohaba station, some 300 km from Lucknow, at 9.30 p.m.
The train then left the station six hours later, he said.
"We have now sent the remains of the explosive device for forensic analysis that will give us an idea about its intensity,' Lal said.