The bodies of two teenage gang rape victims will be exhumed for a fresh autopsy.
Photographs of the two cousins, aged 14 and 15, hanging from a tree in Uttar Pradesh state caused an international outcry in May.
The Central Bureau of Investigation (CBI) has decided to exhume the bodies of the victims after the initial autospy report from the state government was only suggestive of rape without conclusively proving it.
CBI officials have also conducted lie-detector tests on the accused, as well as the fathers of the two girls.
Three suspects have been held, along with two policemen who have been charged with dereliction of duty and criminal conspiracy.
The victims' families said officers took more than 12 hours to respond to reports of their disappearance on the evening of 27 May.
The girls, who belonged to a low caste, went missing from the Badaun district after they went outside to relieve themselves as they did not have a toilet at home.
Their dead bodies were found the following day. The initial post-mortem examination revealed multiple sexual assaults and death due to hanging.
The victims' families say it took police a long time to search for the girls because they were from a low caste.
It is commonly known deep divisions exist between India's castes and violence is often used by upper castes to instill fear in their lower counterparts.
Rape is one of the most common crimes in India. According to the National Crime Records Bureau, 25,000 rape cases were reported in 2012, of which 24,470 were committed by a relative or neighbour.