Inspector Prasad Gautam of Sihanigate police station said investigations are on to nab the culprits who have been on the run since the incident.
However, police said that the blood-stained note could also help them reach the culprits, and they have sent the note to the lab for further tests.
The girl was found dead on Thursday morning in a field along the Nandgram-Sihani Road opposite Mariam Nagar leading to a large-scale protest by family-members and local residents.
Her postmortem report confirmed that she was raped before being killed. To hide her identity, the assailants had disfigured her face.
Police had to lathicharge and fire teargas shells and rubber bullets to disperse protesters.
"Three police teams have been working to nab the culprits. Our main aim is to find all the accused first," Gautam said, adding that several persons are being interrogated in this case.
Meanwhile, former BJP national president and MP Rajnath Singh visited the victim's kin and promised them that justice would be done in this case. Singh said he would raise this issue in the Lok Sabha.