The two persons sprayed "something" on the girl, who had recently come here to a congregation to be trained as a nun, when she opened the door and committed the crime as she became unconscious, a senior police official said.
The girl informed her seniors about the incident who later approached the police, DCP (East) N Satish Kumar said.
A case has been registered at the Hennur police station and the investigation is on. The girl is undergoing counselling at St.John's hospital, he added.
The alleged rape of a six-year old girl student of a public school also came to light on July 15, triggering protests by parents and evoking all-round condemnation and outrage today.