Mohammad Imran was arrested in connection with the death of Zainab Ansari, whose body was found in a rubbish heap more than a mile from her home in Kasur on 11 January.
Police officials say the 24-year-old suspect has confessed to killing Zainab and seven other girls.
Pakistan's chief justice Mian Saqib Nisar has asked detectives to investigate whether Imran was part of a gang supplying videos of children being abused to an international network.
The allegation was made in a local TV news report which reportedly claimed Imran had 37 bank accounts with potential links to a group involved in distributing child abuse images.
A judge at Lahore High Court has granted police another week to question Imran, who has not hired a lawyer to represent him.
Zainab's parents were on a pilgrimage in Saudi Arabia when she disappeared on her way to a Koranic study class a week before her body was found.
Widespread anger over her death led to the sacking of a police chief amid allegations of government inaction and nationwide protests in which at least two people died.
Zainab's father, Mohammed Amin Ansari, has called for his daughter's killer to be publicly hanged, which is currently banned under Pakistani law.