The third student, who is in the hospital, could not be produced before the district magistrate.
Kalburugi Superintendent of Police N Shashi Kumar said that those arrested were identified as Lakshmi, Athera and Vishnupriya.
The victim, a student of Al Qamar College of Nursing School in Gulbarga, is presently in a critical state.
Since the unfortunate incident, the first year student from Kerala has been in hospital with several internal burns. She was shifted to the KozhikodeMedicalCollege after have spent over a week in the ICU at a hospital in Karnataka.
The doctors have reportedly said that the toilet cleaning fluid has burnt the student's internal organs.
The principal of the nursing school, Dr Esther, has said that there was no ragging, adding the girl drank the phenol because of some family problems.
The victim's mother, who is a daily wage labourer, took a loan of Rs three lakh for her daughter's education.
To Gandhiji, wherever he is
A cow hospital with a cancer ward and ICU
The life and times of a modern princess