The suspects include Sher Alam Mehsud, Bashir Ahmad and Inam Ullah.
During the initial investigations, the suspects revealed that they belong to Wana, South Waziristan.
They also claimed that they had come to Karachi in search of a job.
Twin blasts in Shia-dominated Abbas Town, Karachi, on March 3 left at least 50 dead and over 140 injured.
The Supreme Court took suo motu notice of the incident, while police raided different areas in the city in order to arrest those involved.
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