The child's death sparked widespread protests across the city, turning violent after police used firepower to disperse them.
In Lahore, the provincial capital of the state where Kasur is located, protesters blocked a major road connecting the two, causing traffic between them to be suspended.
The official, who spoke on condition of anonymity, said the child named as Zainab was kidnapped on January 4.
Police claim a 6-year-old girl found dead on a rubbish heap may have been raped and held captive for two days before her death.
Officials initially said she was eight years old but her family have confirmed she was just six.
In fact it was not an isolated incident of its kind in Kasur but over the past one year the area has seen about twelve such horrific incidents taking place with minors with local administration appears to be in deep slumber and playing down the magnitude of child abuse, which made the young souls more vulnerable to such incidents.
Sharif, who had assured Zainab's father that justice would be done, also fired Kasur's police chief over negligence in the case, according to a Punjab government statement Thursday. "Today, Pakistan is burdened by the weight of Zainab's coffin", she said.
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"This is the failure of the government", complained one protester.
Mr Ansari had accused the police of being slow to respond after his daughter was reported missing last week. "We do not want such an inadequate system".
The protests continued into Thursday, with Kasur police spokesman Muhammad Sajid saying protestors had "thrown stones on the buildings of the government hospital, police and deputy commissioner's office".
Sajid said that up to 20 suspects had been apprehended "but the investigators have been unable to find any clue so far".
Ihtisham ul Haq, summed up many people's exasperation at a lack of progress in finding the killer.
Civil society, known faces from the entertainment industry and locals in multiple cities have voiced anger and disappoinment in the law enforcement agencies and called for the government to take steps that protect lives of children across the country. The clarification stated that the chief justice had only referred to a news item that had gone viral on social media.
The case has attracted the attention of the country's civilian and military leadership with Punjab Chief Minister Shahbaz Sharif calling for immediate action.