The NIA today took over the custody of three persons arrested in connection with the blast in a passenger train at Shajapur in Madhya Pradesh last week to ascertain their role and the group they were working for.
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.
The NIA took over their custody at a special court in Bhopal for 11 days so that they could be interrogated at length, an official spokesperson said.
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.
However, the police teams engaged in the probe said there was no direct evidence linking the three arrested persons as well as Saifullah to the ISIS.
The accused were produced before Additional District Judge Girish Dixit, who sent them in NIA remand till March 27.
Of the three, Danish (27) and Muzaffar (22) are residents of Kanpur, while Husain (19) is a native of Kannauj district of Uttar Pradesh. They were arrested from Madhya Pradesh's Hoshangabad district on March 7, the day of the blast.
The trio is accused of planting a pipe bomb on the train.