NEW DELHI: In the wake of the CBSE mathematics paper leak, the police have interrogated more than 60 people including the admins of over 10 WhatsApp groups on which the leaked question papers were circulated.

The initial investigation revealed that most of the papers were shared "out of friendship", police said. On being questioned, the students and tutors revealed that they got the papers from someone else.

The police have also sought the details of the e-mail address from Google to identify the source from where the Central Board of Secondary Education chairperson was sent a mail on the Class 10 mathematics paper being leaked.

The Delhi Police Crime Branch had sought details of the examination centres, their superintendents and the contacts of banks where the papers were kept for safekeeping and these have been furnished by the board, the official said.

"The papers (economics and mathematics) were shared on over 10 WhatsApp groups, comprising 50-60 members. These groups were active in outer Delhi and border areas of Delhi and Haryana. Four numbers that the CBSE had mentioned in their complaint were used to circulate the Class 12 economics paper were traced and through them the police traced these WhatsApp groups and their admins," the official said.

The WhatsApp groups mostly comprise students and tutors and some of them had common members, the official said.

"If we are able to establish the link of any of these WhatsApp group members with those connected to officials related to the examination process, we might question the latter as we have got their details from the board," the official added.

The CBSE also informed the police that they had received five complaints informing them that the two papers were leaked, another official said, adding that the contents of these complaints have been shared with them and will be examined.

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 email, the sender had stated that the mathematics paper was leaked on WhatsApp and that it should be cancelled, they said.

The mail also contained 12 images of the handwritten mathematics paper allegedly leaked on WhatsApp, according to the complaint.

In its complaint to the police, the board had said that they received a complaint by fax on March 23 from an "unknown source" that a man running a coaching institute in Rajendra Nagar was involved in leaking the economics paper.

The complaint also named two schools in Rajendra Nagar for their involvement in the alleged leak.

The police said that so far, they have not found any clue to indicate that the schools were involved and it appears that it was an act of mischief. They have also asked the board to share the fax number from which the anonymous fax was received.

Yesterday, the police "interacted" with three officials of the Board -- the Controller of Examinations, Regional director CBSE, Delhi and secretary to understand the examination process and other details pertaining to papers being set.

On March 26, when the students sat for the economics paper, the CBSE Academic unit at Rouse Avenue received an unaddressed envelope in the evening containing four sheets of hand written answers of the economics paper.

The Delhi Police has registered two cases in connection with the leaks. The first case relating to the leak of the economics paper was lodged on March 27 and the other 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.

A Special Investigation Team (SIT) comprising two deputy commissioners of police, four assistant commissioners and five inspectors has been set up to investigate the matter.

The team is being supervised by the joint commissioner of police (crime).

(With inputs from PTI)