However following a complaint by the woman’s family, police formally opened an investigation into Mr Sengar, his brother and more than two dozen others, alleging murder, attempted murder conspiracy and intimidation, the BBC reported.
Federal investigators will take over the case because of fears the local police cannot be trusted.
One of the aunts killed in the crash had been a witness in the case. The woman’s family said it feared for its safety.
“This is not an accident,” the mother told reporters at the Lucknow hospital where her daughter remained critically ill.
“One by one, all the witnesses are being eliminated. We’re afraid for our lives,” said the mother.
Police have arrested the driver and owner of the truck.
The case threatens to embarrass India’s prime minister, Narendra Modi, and his BJP party.
A party spokesman in the state, Rakesh Tripathi, said a disciplinary panel suspended Mr Sengar last year and asked for his explanation. “He has not been sacked yet because the charges haven’t been proven,” Mr Tripathi added.
On Tuesday, protesters tried to march towards the state government’s office in the capital New Delhi as they criticised Mr Adityanath for failing to protect the teen.
“For months the police doesn’t register a case against the politician. Once that is done, her father is killed in police custody and now, a clear attempt to kill her,” social activist and one of the protest’s organisers Shabnam Hashmi told AFP.