The probe agency had swung into action immediately after reports about the train blast came in the morning of March 7 as anti-terror squads of Madhya Pradesh and Uttar Pradesh police started a probe after getting leads in the case.
Three persons Atif Muzaffar, Mohammad Danish and Syed Mir Hussain were arrested jointly by the two police forces, while Uttar Pradesh police killed Saifullah after a 12-hour-long gun-battle at Thakurhunj area of densely populated old Lucknow.
Ten people were injured, three of them seriously, in an explosion on Bhopal-Ujjain passenger train near Jabdi station on March 7.
Madhya Pradesh Chief Minister Shivraj Singh Chauhan had claimed that the blast was the handiwork of the ISIS as some of the accused had uploaded pictures of the blast on social networking site.
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(REOPENS DEL60)
The accused were produced before Additional District Judge Girish Dixit, who sent them in NIA remand till March 27.
The trio is accused of planting a pipe bomb on the train.