India's top investigative agency is due to begin questioning two men accused of killing 17 young women and children in Noida, a suburb of capital Delhi.
The remains of the children were found hidden in bags
Businessman Maninder Singh Pandher and his servant Surendra Koli were handed over to the Central Bureau of Investigation (CBI) on Thursday.
They were arrested two weeks ago after the remains of the victims were found in Noida, a suburb of capital Delhi.
They are being held on suspicion of multiple abduction, rape and murder.
The CBI, which took charge of the probe into the killings on Wednesday, appeared in a court in Noida on Thursday to claim custody of the accused.
The agency has been granted the custody of the accused for 14 days. A CBI team has held meetings with senior police officers to discuss details of the case.
Forensic experts have also visited the businessman's house in Noida to collect more evidence.
Last week, the accused were taken to the western state of Gujarat for tests in a forensic laboratory.
Police control angry crowds outside the house
They were put through several days of tests, including polygraph tests for lie detection and brain mapping.
They were also administered a chemical, known as "truth serum" which, experts say, leads to a state of semi-consciousness and affects a person's ability to lie.
The results of the tests may not be known for some more time as experts at the laboratory say they will need a few days to interpret and analyse the results.
The crime has shocked the country and caused immense grief and public anger in Noida, especially against the police whom many accuse of negligence and dereliction of duty.
Furious residents say police failed to act over the abductions and murders because many of those reported missing came from impoverished families.
The residents say that as many as 40 children have disappeared in the area over the past two years.
Six Noida policemen have been sacked for alleged incompetence over the murders. Three senior officers are suspended.
Officials say that those accused of incompetence will be given an opportunity to explain their case, after which a panel will decide on further action.
There has been rioting around what the press has begun to refer to as the Noida "house of horrors", with police being pelted with stones.
The bar association of Noida has said none of its lawyers will defend the accused in court.