The 16-year-old girl, who was allegedly raped and set ablaze by her boyfriend at Greater Noida's Tigri village on Sunday, died at New Delhi's Safdarjung Hospital on Wednesday, police said.
Her body had suffered 100% burn injuries, police said.
Ashwani Kumar, in charge, Bisrakh police station, said, "She died at about 3.30am. The body has been sent for postmortem at the same hospital. We are waiting for the report. The body will be handed over to the deceased's family after the postmortem. We are in process to change the sections in FIR as charges of murders will be added."
Police have taken Ajay Kumar, 18, under arrest for his alleged connection to the incident. According to the police, the girl and the boy were in a relationship for over two years.
The victim's family had said that Ajay had come to meet the girl at around 2am on Monday on the roof of their house where he raped her and then set her on fire before escaping.
However, Ajay told the police she threatened to burn herself when she caught fire and he tried to save her which resulted in burn injuries on his hands.
Kumar said, "We have the statements of the deceased and the accused. We are constructing the sequence of incident."
Last year in April, Ajay had run away with the girl, police said.
Police have also said they found ambiguities in the statements of the girl as her father said the kerosene container, which was used in the episode, was kept at his house.