The CBSE has also said that its chairperson had received an e-mail about the Class 10 mathematics paper being leaked a day before the exam, police officials said.
The mathematics and economics exams were held on March 28 and March 26 respectively.
The police since yesterday have questioned 35 people, including a coaching centre's owner, 18 students and some tutors, in connection with the case, an official privy to the investigations said.
On Thursday, police personnel also "interacted with the CBSE controller of examination for two hours" to understand the process of conducting exams, he said.
The official said things like how the paper is set, details of where the question papers are kept and how they are distributed to various examination centres were discussed.
The Delhi Police has registered two cases. The first case in connection with the leak of the economics paper was lodged on March 27 and the case pertaining to the mathematics paper was lodged on March 28, following a complaint by the regional director of the CBSE.
The cases were registered on charges of criminal breach of trust, cheating and criminal conspiracy.
In the complaint pertaining to the mathematics paper, the board has said that a day before the exam, an e-mail was received on the CBSE chairperson's official ID informing about the leak, the officials said.
In the mail the sender had stated that the mathematics paper was leaked on WhatsApp and that it should be cancelled, they said.
The mail also contained attachments of the handwritten mathematics paper allegedly leaked on WhatsApp, according to the complaint.
A Special Investigation Team (SIT) comprising two deputy commissioners of police, four assistant commissioners of police and five inspectors has been set up to investigate the matter.
The team is being supervised by the joint commissioner of police (crime).
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