While investigating earlier cases of rape and murder of children in Kasur, the police had claimed to have interrogated 5,000 suspects. On January 9, five days after she went missing, labourers found her body from a trash pile.
The IGP was apprised about the actions taken by the police to trace the culprits, an official said, adding that the DNA report, the arrests of the suspects, CCTV footage of the suspect and other aspects of the case had come under discussion.
Kiran Naz, a news anchor on Pakistan's Samaa TV, hosted Thursday's bulletin with her young daughter on her lap as an act of protest.Opening her segment, she said: "Today I am not Kiran Naz, rather I am a mother today and that is why I am sitting with my daughter."Referring to Zainab, she said "the smallest coffins are the heaviest, and the entire society is burdened by the weight of her coffin".
Zainab's death comes less than three years after a scandal in Kasur when at least 280 children were filmed being sexually abused by a gang of 25 men, who blackmailed their parents by threatening to leak the videos.
Zainab's parents returned from their pilgrimage on Wednesday but they were unable to attend their child's funeral prayers.
A source in the Punjab Forensic Science Agency (PFSA) told Dawnthat the agency had received samples collected by Kasur police from the crime scene.
"Up to 1,000 protesters are in the streets", Kasur police spokesman Muhammad Sajid said.
"Naturally, there is also a certain amount of time that the processing will take; there is a certain amount of time that the lab takes", he said.
People from other parts of the country took to social media to share their anger and outrage over the murder using the hashtag #JusticeForZainab. Actress Mahir Khan and Sanam Saeed were among celebrities who staged demonstrations and protested.
"All institutions must work together, and implementation of laws must be strengthened", he said.
It is the 12th such murder in the town of Kasur in a year, and has raised concerns that a serial killer may be on the loose.
Laws for the protection of children must be made in line with worldwide laws, he said.