The suspects, including an official and worker of a political party, have been shifted to an unknown location.
Investigators were also planning to use the geo-fencing technique to get a breakthrough in the case since they could not find any closed-circuit television (CCTV) footage related to the untoward incident.
The gunmen who killed two Pakistan army officials were aware that the CCTV cameras in the area were not working, claimed the investigation officials.
Surprisingly, they were also forced to evaluate that why the CCTV cameras near the Parking Plaza went off exactly an hour before the firing incident and were on when the gunmen fled from the crime scene.
Gunmen on Tuesday killed two army officials in Karachi, where paramilitary forces have been cracking down on militants and criminal gangs for almost three years.
Meanwhile, police have sent the samples from their bodies to a forensics lab expanding the scope of their investigation.
The killings are the latest attack in the busy port city, where one of the most popular singers of Sufi devotional music, Amjad Sabri, was shot dead on June 22.
Police said the soldiers, who belonged to an intelligence agency, were patrolling a crowded area of the southern city when their vehicle was attacked.
“The attackers were on a motorcycle and managed to escape through the congested narrow lanes,” said senior police officer Raja Umar Khattab.
Amid condemnations, both the military officials have been laid to rest with military honour.
Better security in Karachi has been one of the showcase successes of the crackdown, although two days before Sabri’s killing, the son of the provincial chief justice was kidnapped from an upscale shopping area. He was rescued later.
Karachi’s murder rate fell by half after the paramilitary Rangers, who answer to the Ministry of Interior and the army, launched the crackdown in 2014, targeting suspected militants and criminals.
The latest terror incident happened on the eve when Pakistan People’s Party (PPP) leader, Syed Murad Ali Shah was nominated as the new Chief Minister Sindh who has cited maintaining law and order in the city as the biggest challenge for the provincial government.