CBSE paper leak: The investigations by the police into the leak of two question papers in class 10 and class 12 exams conducted by the Central Board of Secondary Education has WhatsApp at the centre of the breakthroughs so far. It is believed that Whatsapp, the most popular messaging app in India, played a crucial role in the police investigation leading to the arrest of two teachers over their alleged involvement in the entire paper leak scandal. The probe has been complex and the police only had the leaked Class 12 Economics paper as evidence. The police have so far registered two cases in the CBSE paper leak matter. While the first case pertaining to the leak of the class 12 Economics paper was lodged on March 27, a day after the paper was held, the other case regarding the class 10 Mathematics paper was lodged on March 28, the same day that the exam was held. According to the police, both cases were filed following a complaint by the regional director of the CBSE. In its complaint to the police, the CBSE 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, reported PTI. The probe began under Deputy Commissioner of Police Ram Gopal Naik who led a special crime branch investigation team. On their hands was a case related to possibly the biggest crisis that the CBSE, as well as lakhs of students, were in the midst of. The probe began with the details of 4 Whatsapp groups where the leaked paper where shared. The details of the groups were mentioned on the tip-off that was received by the CBSE and proved crucial in the probe by the police. As per reports, the police was able to decode the message chain after it found that one of these four WhatsApp groups was allegedly being run by a teacher of a prominent school. With the help of that one group, the police then traced the message trail and reached the origin of the message. A senior investigator said that they were able to identify the person who had posted the question paper in that group. And through that one person, the police was able to follow the message chain and trace it to 20 other phones. The probe, however, hasn't been a smooth sail. While tracking the message trail, the investigators hit a roadblock when they found the message chain broken as the message was either deleted or they were not able to identify the specific group that had received the leaked paper. The investigator said that in most cases, while the receiver had already deleted the message, it was still available on the sender's phone. The image of the leaked paper, which carried the paper code which is mentioned at the corner of the question helped the police to narrow down the search of the school from where the paper was originally leaked. The code on the photo further led the police to the class 12 student who turned out to be the direct beneficiary of the whole leak. The investigator said that the boy had received the paper from a tutor identified as Tauqeer Hasan who taught at a coaching centre. The police then nabbed Hasan from Ghaziabad and he went on to reveal that the paper was sent to him by Rohit who is a Mathematics teacher at Delhi's Mother Khazani Convent School, cops said. The police revealed that while Rohit had sent the paper to Hasan, he did it at the behest of his colleague Rishabh who is a Physics teacher at the school. The two teachers had accessed the paper over an hour before when the exam was to take place. Alok Kumar, the Joint Commissioner of Police, revealed that the investigation was taking place to determine the origin of the paper leak. Other senior police officials said that the leak had taken place inside the Mother Khazani Convent School. Meanwhile, the news about the paper being leaked from the school has been denied by the school chairman.