Dipak Fernando was arrested last night, while hunt was on to nab two other accused Aftab Ahmad and Rashmi Kanpur, Superintendent of Police Anil Kumar Singh today said.
Yesterday, the agitated crowd allegedly vandalised the college premises and assaulted the accused teachers.
Following which, the principal lodged an FIR against 300 unidentified persons, he said.
The girl, student of the private intermediate college, was under depression and allegedly set herself afire in Kotwali area on Friday after which she was admitted to a hospital where she died on Saturday night.
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On the basis of this, the victim's father had lodged an FIR against the three teachers on Sunday.
In the complaint, it has been alleged that Deepak Kumar teased the girl about which a grievance was lodged with the college authorities, but no action was taken.
The accused teachers have been suspended from the college after the incident, the College Principal Villiam Pinto said.
Yesterday social organisations and locals also held condolence meeting and candle march to protest against the incident.