Intelligence personnel during a raid at an under construction seminary in Samnabad nabbed the suspects. They were identified as Zahid, Asim and Ghaffar.
The suspects Zahid and Asim happen to be brothers, while the third suspect Ghaffar is their cousin.
They had allegedly provided refuge to terrorists involved in the Gulshan Iqbal Park bombing that killed over 70 people and wounded nearly 300 on March 28.
Officials are investigating them about the terrorists who carried out the deadly blast, the place where they came from and about the one who provided explosives.
The suspects are expected to make some more revelations.