The youth, who has been detained, so far claimed that he found the body of Nikita after returning home from work and gave some leads to the investigators which helped them zero in on the prime suspect, a senior police official said.
The prime suspect is believed to be a close friend of the youth. He is being tracked by a police team, and they said, since last night he has been shifting his location in Delhi-NCR and western UP.
Nikita's identity was ascertained with the help of an identity card recovered from the room. She had sustained four stab injuries -- two on her abdomen and two on arms.
A case of murder has been registered, police said.
Nikita, a school dropout, lived with her family in central Delhi's Anand Parbat area. Her father is a plumber.