After Chief Justice of Pakistan Mian Saqib Nisar took suo motu notice of the brutal murder of six-year-old Zainab in Kasur, Inspector General Punjab Arif Nawaz Khan submitted a report to the Supreme Court on Thursday saying that 272 suspects have been questioned about the incident.

The report said that geo-fencing data from the area was acquired and all resources are being employed to catch the culprit. It also said a house-to-house search was being conducted based on the information provided by the last witness of the crime.

It said that a case had separately been registered regarding the incident of firing on people protesting Zainab's murder. Sections 302 and 201 of the Pakistan Penal Code (PPC), which deal with wilful murder and wiping out evidence, have been included in the first information report (FIR) of the incident, the report said.

A post-mortem examination of the victim, who went missing on Jan 4 and was found dead in a trash heap by police on Jan 9, suggested she was raped and strangled to death. DNA samples collected from her body have been sent to a lab in Lahore for forensic testing ─ a process that can take up to three months.

Explore: 6-year-old Zainab's autopsy suggests child endured rape, captivity before murder

The victim's family yesterday accused the police of being un-cooperative when they were alerted that Zainab had gone missing.

Punjab Law Minister Rana Sanaullah told DawnNews earlier today that the joint investigation team tasked to investigate the murder has been in touch with the family and will work closely with them to solve the case.

He added that at least four people have been taken into custody for "investigation purposes", but no formal arrests had been made in the case as yet. "We are hopeful that the culprit will be caught very soon," the minister said.

The brutal murder of the girl is the 12th such case to occur within a two-kilometre radius in the city over the last year.

The surfacing of a series of similar cases since 2015 have led police to believe that a 'serial killer' is behind the horrific rapes and murders of minors in Kasur.

Police believe 'serial killer' behind murder

An initial probe indicates that a 'serial killer' was behind all eight cases reported in the district since 2015.

A rudimentary sketch of the suspect had been prepared by police in 2015 with the help of a local who spotted him as he was going to assault a minor girl in an under-construction house.

A police official told Dawn that more incidents of abduction of children, including five girls, occurred in Kasur district ─ all of which were reported within the jurisdiction of three police stations – A Division, B Division and Sadar.

Three out of the eight cases, including the latest one, occurred recently.

The official said a team of senior police officers had last year attempted a detailed analysis of all the cases in the light of circumstantial evidences, DNA test reports, statements of the two girls who survived the assaults, the witnesses and other relevant information.

The efforts were prompted in July 2017 when a case similar to Zainab's surfaced.

The officers had concluded that a single person was behind all the cases surfacing in the district.

The view was strengthened when the investigators found a close resemblance between the man in the CCTV footage of Zainab and the culprit’s sketch in the police record.

"We had started the hunt for the serial killer shortly after the first case in 2015," the police official said.

"We had got reports of five DNA samples sent to the lab for analysis and the reports showed they belonged to the same person," the police official said.

[A reward of Rs10 million][4] has been announced by the Punjab government for anyone who can identify Zainab's killer.

With additional reporting by Asif Chaudhry.