A court in a suburb of the Indian capital, Delhi, has extended the remand period of two men accused of killing 17 young women and children by two days.
The remains of the children were found hidden in bags
The businessman and his servant have been taking polygraph lie-detector tests in the western state of Gujarat. They are due in court on Friday.
The two were arrested 10 days ago after the remains of the victims were found in a sewer in the suburb of Noida.
They are being held on suspicion of multiple abduction, rape and murder.
On Wednesday, India's top investigative agency, the CBI, took charge of the probe into the killings.
A prosecution lawyer, appearing on behalf of the police, told a court in Noida that businessman Moninder Singh Pandher and his servant Surender Koli could not be physically produced before the court.
Police control angry crowds outside the house
He said the two men were undergoing more tests in a forensic laboratory in Gandhinagar, capital of the western state of Gujarat.
The two accused have been put through five 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 director of the laboratory, Dr JM Vyas, said the two men co-operated during the tests.
He said they will undergo a medical examination before they return to Noida.
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 laboratory in Gandhinagar is one of the few in the country with the facilities for such tests.
Police say these tests will help them in their investigation and hope they will provide vital clues.
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.