Judge A K Singh granted the remand after an NIA-team probing the Patna serial bomb blasts of October 27, 2013, produced the four before its special court here.
The suspects Haider Ali alias Black Beauty, Numan Ansari, Mojibullah Ansari and Taufiq Ansari were brought by a special flight to the city and produced before NIA Judge AK Singh at his residence late in the afternoon after the court had closed for the day, police sources said.
Of the four suspects nabbed from Ranchi and Daltonganj areas of Jharkhand, Haider was said to be running banned terror organisation SIMI, while Numan, Taufiq and Mujibullah were allegedly involved in bomb blasts in the city and Bodh Gaya.
They are among the 13 arrested so far in the serial blast case at Narendra Modi's rally here last year.
At least seven people were killed and scores others injured when bombs exploded at a make-shift railway platform and at the rally of Modi.