The gang allegedly abducted and sexually assaulted at least 280 children in the area, blackmailed the families of the victims since 2009, and even sold video clips and images of the assault.
Riots erupted in Kasur over police inaction after reports of the alleged rape and murder of the girl began circulating on social media.
The bench had summoned IGP Arif Nawaz Khan while hearing a petition moved by a lawyer, Shaheen Pirzada, seeking direction to the government for proper legislating to control incidents of children's abduction, rape and killing.
The IGP told the court that a total of 11 incidents of rape with minor girls had occurred during the last two years in the district. This led to violent protests in Kasur during which two people died and several acts of vandalism took place. It is not clear yet whether the policeman was responsible for the deaths or injuries.
On January 4, Zainab had left her house to go to her maternal aunt's nearby and is believed to have been abducted en route.
Zainab was kidnapped from Road Kot area in Kasur while her parents were in Saudi Arabia to perform Umrah. Her body was later found in a garbage pile near her home.
The hearing in the case has been adjourned till Jan 15.
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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 father, Ameen Ansari, told the BBC that he did not agree with the violence of protesters, but understood the anger at police."If the police had done their jobs properly then they would have found her as soon as they got hold of the CCTV", he said. "We are now afraid of letting our children leave the home".
Police earlier told Dawn that DNA samples from the victim's body have been dispatched for forensic testing.
Zainab's medical report confirmed ample evidence of assault and rape on the little girl's body.
Punjab Chief Minister's advisor Dr Umer Saif published the report pertaining to the developments made in the case.