Sources said Vicky, who runs a coaching center in Rajinder Nagar, will be quizzed again on Friday after being let-off on Thursday night.
Some of the tutors teach at home while the others are employed at coaching centres. There are also first-year college students, who passed on the papers to their juniors, or friends from school or coaching centres.
The police, however, failed to get any significant leads so far in the case.
Special Commissioner of Police (Crime) R P Upadhyay said: "Currently, the investigation is based in Delhi. We have no information that this leakage is pan-India. If such a thing emerges (about leakage being outside Delhi), we will send teams outside Delhi."
The crime branch has also asked three CBSE officials to brief it about the process the examinations conducted by the Board.
"The Board has been cooperating in the probe. We have asked them things like how the paper is set, details of where the question papers are kept and how they are distributed to various examination centres. After we get these details, we will try to find out how the leak happened," Upadhyay was quoted by PTI as saying.
The CBSE had said it will conduct re-examination in the Class 10 mathematics and Class 12 economics subjects following reports of paper leaks. The Board is likely to announce the re-test dates on Friday.
The government has said the difficulty level of examinations will remain unchanged.
This would be the first nationwide retest in recent memory. The scale could have been minimised had the CBSE retained its policy of drafting different question paper sets for different regions. The call for a nationwide retest has fuelled suspicion that the board had opted for a composite paper.
Officially, the Class XII exams will end on April 13 and the Class X exams on April 4. But for many Class X students, Wednesday's math paper was the last exam as the remaining subjects range from Sanskrit to painting.
Hours before the math exam was to begin on Wednesday morning, the questions were available on WhatsApp groups. Several parents in Delhi later complained that the questions circulated on social media were in the same sequence as they appeared on the question paper.
The questions asked in the Class XII economics exam, held on Monday, were available on WhatsApp before the test.
The CBSE, which falls under the administrative control of the HRD ministry, has taken up the issue with Delhi police.
Meanwhile, the Congress party demanded that Union HRD Minister Prakash Javadekar and the CBSE chairperson be sacked.
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