The principal of a school, whose two teachers were arrested for their alleged role in leaking class 12 economics paper, was grilled today for over six hours by the police, along with the arrested accused, said an official privy to the probe.

The police have also started investigating whether the papers were leaked from Haryana since some clues have emerged that the papers might have been leaked from there, he said.

The police have ruled out the possibility of collusion of the suspended CBSE official with the accused since they found nothing to indicate his involvement.

"The official was negligent in delivering the papers early but so far, we have found nothing to indicate his connivance," the official said.

"However, he had delivered the papers of all the subjects before the scheduled time which means that the accused could have circulated other papers too. We are questioning them to ascertain whether they were involved in leaking other papers too," he said.

Meanwhile, the police today quizzed the arrested teachers, Rishabh, 29, and Rohit, 26, of the Mother Khazani Convent School in Bawana, and private coaching centre tutor, Tauqeer, 26, along with the school principal.

The four men were first questioned separately and later they were quizzed together to ascertain whether the principal had any idea about Rishabh and Rohit's actions, he said.

Some loopholes were found in their versions which indicate that the principal might have been aware about the teachers allegedly leaking the economics paper.

The police have also started looking into some places in Haryana and are probing whether some CBSE officials or schools in Jhajjar, Sonepat, Bahadurgarh, were involved in leaking the papers.

"The papers were mostly circulated in outer Delhi and areas bordering Haryana," the official said.

The Delhi Police has lodged two cases over the leaks of the CBSE question papers.

The first case related to the leak of economics question paper was lodged on March 27, while the other pertaining to the leak of mathematics paper was lodged on March 28, following a complaint by the CBSE's regional director.  -- PTI