The first incident was reported from West Delhi's Hari Nagar when police received a call from Deen Dayal Upadhyay (DDU) Hospital regarding a 16-year-old girl who was brought in dead by her father.
A senior police officer said the three deceased have been identified as Udhan, Kamlesh and Parmod, all labourers on their way to Delhi from Shahjahanpur.
Police arrested Kumar in 2015 in connection with the Northwest district case. The victim's body was found in an under-construction three-storey building.
Four men were arrested after Jangra took to twitter and requested the Delhi police to take action. The incident took place on 8 May near Nangloi Railway Station