New Delhi: After the arrest of two teachers of a Bawana school and a tutor of a coaching centre in the same area on last Sunday for allegedly leaking the CBSE Class XII Economics exam questions, Delhi Police interrogated the principal of the school on Monday. The principal told the police that the video recording device connecting all 15 CCTV cameras in the school wasn't working.

It was revealed that the leaked question paper had reached the exam centre (the Bawana school) two hours before the March 26 test which is a gross violation of protocol. CBSE official K S Rana, suspended on Sunday for laxity in supervision at the centre, would be quizzed on Tuesday.

The accused might have been involved in leaking CBSE question papers earlier too, police sources said. They aren't discounting the role of a syndicate involving some Board officials. The possibility of other question papers having been leaked this year has also not been ruled out.

The Delhi crime branch is also focusing on the module that leaked the Class X Mathematics questions. The paper was circulated in four WhatsApp groups each comprising more than 60 members each. Cops contacted a complainant who had sent the copies of the leaked papers to the CBSE chairperson, but he could not provide details about the source of the leak. A tutor and some schools in west Delhi are under the scanner.

According to protocol, question papers are stored at government banks a day before the exam and taken to the centres by CBSE officials called 'custodians'. The papers are kept in custody of the principal of a school (exam centre) and the seal is broken only after students are seated at the hall. However, it was found that the arrested teachers of Mother Khazani Convent School, Bawana had met three students on the school premises an hour before the Economics exam