Police arrested a suspect on Thursday who they accused of facilitating the attack which killed seven policemen in Orangi Town.
The suspect who was arrested during a search operation in sector 11½, Orangi Town has been transferred to an undisclosed location for interrogation, sources said.
The suspect belongs to a banned militant outfit and 11 of his accomplices are in jail, sources said.
Security forces are conducting door to door searches at Orangi Town where seven policemen deployed on guard duties for an anti-polio campaign in the area were killed on Wednesday.
Police conducted a search operation in several areas of Orangi Town late night on Wednesday.
During the search operation, 18 suspects including a woman were taken into custody.
An FIR for the Orangi Town firing incident was registered at the Pakistan Bazaar Police Station on Thursday.
The FIR includes murder and terrorism charges.
The geofencing of the incident has been done, and sketches of the attackers are being prepared with the help of CCTV footage.
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