The girl's parents are migrant labourers from Bihar, while the accused boy was now residing with his uncle, who also hails from the same state.
The half-naked body of the minor, who was missing since last Tuesday after she left home for tuition classes, was found with injury marks near a canal in Budhakhera village of Jind district.
Police had detained the boy's parents for questioning following the discovery of the girl's body on Saturday, but both of them have now been released, the official told Hindi's Manoj Dhaka.
Asked about the allegation levelled by the girl's family that the local police did not immediately act on the complaint lodged when the Class 10 girl went missing, the Kurukshetra SP said the SHO concerned had been placed under suspension.
Two of the girl's neighbor, 28-year-old Pradeep Kumar and 22-year-old Sagar have been arrested after police carried investigation. In one case, the private parts and internal organs of the 15-year-old victim were inflicted with wounds, while in another the accused committed necrophilia on the minor victim of 11 years.
After that, the police have discovered the dead body of a boy who was a prime accused in Jind rape and murder case. The crime took place when the girl's parents had gone out to work.
The extent of the 15-year-old victim's injuries led many to draw comparisons with the 2012 gang rape and murder of a Delhi physiotherapy student.
Chief Minister Manohar Lal Khattar described the incidents as "unfortunate" and said: "We'll take strict action and tie up all the loose ends".
The role of the police, he continued, was to "investigate, catch criminals and prove things" and "we're leaving no stone unturned". Alleging that lawlessness prevails in the state and there was a complete breakdown of the law and order machinery, the Congress urged the Governor to recommend to the Centre to dismiss the Khattar government.
'At least four men are suspected to be behind the crime, ' said district police chief Abhishek Garg. The cop's insensitive remark comes at a time when there have been four major rape cases in Haryana in the last four days.