According to the post-mortem report, Shah was also kicked in her genitals, which caused serious injuries, Express Tribune reported.
The news report quoted a police official, who spoke on the condition of anonymity, that they are awaiting polygraph and DNA test reports from Punjab Forensic Science Agency (PFSA). According to him, the reports can ascertain if the victim was also sexually assaulted.
He further said that the suspects are detained at the Adiala jail on judicial remand.
On June 3, Shah was beaten up by her employer in Rawalpindi, identified as Hasan Siddiqui, and his wife Umme Kulsoom in Rawalpindi.
The maid was brought from Muzaffargarh four months ago. Siddiqui, who had hired the child, worked as a bird buyer and seller. The incident came to the fore when the man brought her to a local hospital, leaving her there. She was immediately placed on a ventilator, but could not survive.
In September last year, a teenage boy Hunain Bilal died after being severely beaten by his teacher in Lahore, police had said.