Breaking silence for the first time since the government admitted a paper leak, CBSE chief Anita Karwal said: "We are working for the children. We will also announce the dates very soon. Nobody needs to worry. We have taken a decision in favour of the children".

Union minister Prakash Javadekar said the dates for the fresh exams will be announced by Monday or Tuesday. "I also could not sleep. I am also a parent," the minister added.

The board had been fending off complaints for days that question papers were leaked. The FIR shows it received a fax on March 23, two days before the economics exam. They informed the police the next day, but the exam was not called off. A case was filed on March 27, a day after the exam.

The case names the head of a coaching centre in west Delhi's Rajinder Nagar. The police said they recovered snapshots of the handwritten question papers, which were being circulated on WhatsApp, from him. They are trying to trace the source of the WhatsApp messages, but are facing problems because of the end-to-end encryption.

The police have questioned 18 students. 11 from various Delhi schools and seven first year college students. Five tutors of the coaching institute and two others have been questioned as well. The police they had the handwritten question papers a day before the exam.

The investigation is currently focusing on the role of CBSE officials, invigilators and school staff, coaching centres and printers. But officers investigating the case say they are yet to question anyone from the CBSE or examination centres. The questioning will begin once the source of messages is traced.

With the CBSE leak occurring a month after SSC papers leak, the government came under opposition attack. Congress chief Rahul Gandhi tweeted: "The exam leaks destroy the hopes and futures of millions of students. The Congress always protected our institutions. This is what happens when institutions are destroyed by the RSS/BJP. Believe me when I say, this is only the beginning."

"I really feel sorry and sad for the students who have to give their exams again for no fault of theirs. Responsibility shud be fixed n strict action shud be taken against those responsible," Delhi Chief Minister Arvind Kejriwal tweeted.

The leaked economics paper was being circulated on social media, including WhatsApp, several hours before the test started on Monday. On March 15, the Delhi government said it received complaints from the CBSE about the Class 12 Accountancy paper being leaked.