Bengaluru, Dec 1 : The preliminary probe by police has revealed that the bomb threat emails sent to over 15 schools in Bengaluru have some jihadi content, said sources on Friday. Sources said the letter stated, "Convert to Islam or die under the weight of sword of Islam. Bismillah, we will spread the true religion of Allah to the whole of India." "You have choice to become our slaves or accept the true religion of Allah. Temples, your idols, from Buddha to infinity, they will fly apart from our explosions," the threat email claimed. The email further stated that there were explosive devices in the school premises. Referring to Mumbai terror attacks, the email claimed that "on November 26, martyrs in the way of Allah killed hundreds of idolaters. It is truly powerful to hold a knife over tens of millions of kafirs". The authorities said that the communal writing in the letters has made them take a serious note of the development. They also stated that it might be the handiwork of a prankster as well. The investigation will reveal everything, sources said. On Friday morning, more than 15 reputed schools received bomb threats through email on their official email Ids. The incident had triggered tension and concerns in the city. Deputy Chief Minister D.K. Shivakumar, reacting to the media over bomb threats, appealed to the people not to panic. "Few will indulge in such acts. We need to be careful. Cyber crime police are doing their job well. Police have taken immediate action. Earlier, a person who got late to flight had given a bomb threat," he said. /IANS