The private schools received threats on Monday at 2.49 a.m. The searches started at 6 a.m. and continued till late night hours.

After extensive searches, the threat turned out to be a hoax as nothing suspicious was found in any of the schools.

The bomb threat was sent from a mail ID '[email protected]' via the Russian domain.

Police are investigating the matter and analyzing the language of the emails. The wording of the email sent to Delhi schools and airports recently is also being studied.

Preliminary investigation has revealed that Russian servers have been used for sending the threat mail to Jaipur and Delhi schools. An email was sent to the schools of Delhi from the id '[email protected]' and to the schools of Jaipur from the id '[email protected]'.

Meanwhile, cyber experts said that criminals generally have been using VPNs from other countries to hide their location. “For example, in both the Jaipur and Delhi cases, it is being said that emails were sent from the Russian servers. It is possible that the emails were sent from some other place, but the location is shown as Russia,” they added.

Cyber security expert Mukesh Chaudhary said that by hiding the location through VPN, such accused manage to escape from the police.

"Anyone can change their location through a VPN. In such a situation, the email receiver feels that the sender of the email is in the same country from where he has received the mail, however, the case is different," he said.

Meanwhile, officials did not deny a strong possibility that some organisation or gang may be behind the incidents in Delhi and Jaipur.

Jaipur Police Commissioner Biju George said that a similar pattern of mail has been used in Delhi and Jaipur schools. There is no dateline mentioned and it uses the term Bcc under which one mail is being sent to many others. So one should not be scared of such emails.

Cyber security and law expert Monali Krishna Guha said that vicious criminals usually use darknet or proxy servers while sending such emails due to which the police investigation takes a long time to reach any conclusion.

Rajendra Prasad, former in-charge of the cyber crime police station, says that police should take help from the CBI and Interpol when VPN is being used.

The email sent to schools spoke of taking revenge. It referred to Gujarat and threatened to turn cities into ruins.

It needs to be mentioned here that miscreants have sent bomb threats to Jaipur airport six times in the last six months. In May, such bomb threats were sent twice on May 3 and then on May 12. However, no suspicious object was found during the search operation.

In April too, Jaipur Airport received bomb threats on February 16, April 26, April 29 and December 27 last year.