Police on Thursday night said that the autopsy report indicated rape had not occurred in the Krishnanagar death case while a doctor said that burn marks found on the girl’s body were ante-mortem or before death.

The autopsy and forensic reports, however, have not been made public yet, the police said, although a senior officer told The Telegraph that they were privy to the contents.

The girl’s death was caused by carbon gas from the fire, which blocked her throat, the police officer said. The fire was caused by ignited kerosene, with a kerosene container and matchbox found near the body and examined by fingerprint experts.

However, it has not been ascertained so far who ignited the fire, and whether the girl committed suicide or was murdered.

The Class XII student’s boyfriend Rahul Bose, 24, was arrested on Wednesday. A Krishnanagar court remanded him to seven days in police custody on Thursday.

Rahul, who works in an Odisha-based hotel, revealed details about their relationship during questioning, admitting he was planning to break up with her, but denied any role in her death.

According to the girl’s family, she left home on Tuesday night. Her partially charred body was found near a Durga Puja pandal in Krishnanagar early on Wednesday.

A post on her Facebook page suggested suicide.

However, her family claimed that the girl was “gang-raped and murdered”, with her body set on fire to destroy evidence.

Medical superintendent Soumyajyoti Bandyopadhyay, a teacher in the department of forensic medicine and toxicology who oversaw the autopsy, told journalists: We found ante-mortem burn injuries.”

He declined to reveal further details, including whether rape had occurred.

Sources at JNM Hospital said no strangulation marks or other injuries were found on the body.

On Thursday, the Bengal government formed a special investigation team, led by Krishnanagar police district chief Amarnath K. and supported by the CID, to probe the case. Additional director general (south Bengal) Supratim Sarkar said the team would leave no stone unturned in finding out the truth.

Late on Wednesday night, the CID joined the local police in interrogating Rahul who is yet to admit to murder. The police also questioned two others, including a mutual female friend of the victim and Rahul.

Preliminary evidence has suggested that the girl and Rahul were together between 10pm and 11.30pm on Tuesday.

Rahul purportedly admitted that despite tensions in their relationship, he called her around 10.15pm to meet her. After an argument, the girl sent tearful voice messages to her mother. A “goodbye” post, suggesting suicide, on her Facebook account followed later, but investigators are unsure if it was she who posted it or Rahul.

A “loan” of ₹40,000 given by Rahul to the girl seemed to be the cause of the tension between the couple. Rahul wanted the money back to buy a motorcycle. The girl, suspecting he wanted to break off with her, was buying time and not returning the money.

Supporters of the DYFI and the BJP demonstrated outside the Kalyani hospital during the autopsy. The SUCI staged a protest in Krishnanagar, demanding justice for the girl.

Several Trinamool leaders called Rahul a “hypocrite” for joining the Reclaim the Night protests in the wake of the RG Kar crime and demanding chief minister Mamata Banerjee’s resignation.