The Delhi police have collected a week’s worth of CCTV footage from St. Columba’s School as part of the investigation into the death of its 16-year-old student by suicide on November 19, a senior officer said on Friday.

The student took the extreme step following “mental harassment”, sparking protests by parents and students outside the school in Ashok Place near Gole Market on Thursday. Protests outside the school continued on Friday.

A day after the incident, the police registered a case under Bharatiya Nyaya Sanhita sections pertaining to abetment to suicide and common intention against three teachers and the headmistress for alleged ill-treatment of the Class 10 student who had named them in a note recovered from his bag.

The police have summoned all four, who were placed under temporary suspension following Thursday’s protests, for interrogation.

On Friday, the police questioned five of the deceased student’s classmates, some of whom were also named in the note as witnesses to his harassment, the officer said.