She was pregnant when the incident took place, according to the police.
Chief Secretary Sanjay Mitra on Thursday "strongly deplored" attempts to "play politics" over the girl's body, and denied medical negligence in her treatment at a government hospital, while Chief Minister Mamata Banerjee smelt a conspiracy.
Mitra refused to answer media queries and limited himself to reading a statement at the state secretariat.
"The government is fully with the bereaved family. However, at this point I wish to deplore... strongly deplore the tendency to play politics over a dead body," Mitra said.
The teenager was gang-raped twice in October
"There is no evidence of medical negligence. A six-member medical board was looking at the girl. She was in the trauma centre and isolation ward. Finally, she died of multiple organ failure due to extensive burns... around 65 to 70 percent burns."
"The state government and police are totally cooperating with the family. We also provided assistance in her last rites... what they had asked of us," said Mitra, in the wake of criticism of police who had allegedly taken away the girl's body by force for cremation, but had to relent after the parents refused to hand over the death certificate.
Additional Deputy Commissioner (Airport Division) of Bidhannagar police commissionerate Nimbalkar Santosh Uttamrao said: "The doctor treating the girl told us she was pregnant at the time of her death. We have sent the foetus to the forensic science laboratory for determining its age and parentage." .
He said the girl - the daughter of a taxi driver from Bihar - was pregnant when she died.
Meanwhile, the West Bengal government continued to come under attack from the opposition and civil society for the "shameful incident".
Police have already slapped murder charges against two accused, now under custody, based on the girl's dying declaration that the duo had set her ablaze.
The body was finally handed back to the family, who cremated her. The teenager was gang-raped twice in October. She breathed her last Tuesday at the government-run R.G. Kar Medical College and Hospital where she was admitted with severe burn injuries Dec 23.
In Patna, Bihar Chief Minister Nitish Kumar condemned the incident, and announced an ex-gratia grant of Rs.1 lakh for the girl's family and deputed a top police official to meet her parents in Kolkata.
Bihar Police Director General (Special Branch) G.S. Gangwar called on the family, and listened to their tale.
The Left Front brought out rallies and processions in various areas of Kolkata and in the districts, condemning the incident and the "disgusting role" played by police. The Congress also hit the streets.
A section of civil society members held a meeting at the Rabindra Sarobar compound, protesting the incident.
With IANS Inputs