A day after 16 schools in Delhi received bomb threats via email, police said they have apprehended a student from a private school in connection with the investigation. Authorities claim the student’s questioning led to crucial evidence suggesting he is part of a group that has been sending bomb threats to schools for several months, reports The Indian Express.

Police are verifying the evidence with forensic experts before taking further legal action.

A senior officer with the Delhi Police confirmed that they have apprehended one student and said they are investigating the involvement of others.

On Wednesday, officials from the Delhi Fire Service said Tagore International School was the first to report a threat at 11:17 AM, followed by Bluebells School International at 11:40 AM.

Police said the email was sent to Mothers International School, Modern School, Springdale School, G D Goenka Public School, St Columba’s School, Salwan Public School, Amity International School, Air Force Bal Bharati, Delhi Public School in Vasant Vihar and RK Puram as well as Frank Anthony Public School, among others.

The email also warned of “massive and highly dangerous explosives” being present on its premises.