Delhi Fire Services on Sunday said seven city hospitals and IGI Airport received bomb threats through emails, 11 days after over 150 schools in Delhi-NCR received a bomb scare of unprecedented scale.

The bomb threats were reported from Indira Gandhi International Airport Terminal-3, Burari Hospital, Sanjay Gandhi Hospital, Guru Teg Bahadur Hospital, Bara Hindu Rao Hospital, Janakpuri Super Speciality Hospital, Deen Dayal Upadhyay and Dabri's Dada Dev Hospital, a senior official of the Delhi Fire Services (DFS) said.

According to the police sources, the airport authorities received a threat email at 6 pm.

Security has been beefed up in all the hospitals in the city and additional police force deployment was made at the airport, however, nothing suspicious was so far recovered from any of the locations so far.

After a call regarding the threat from Burari Hospital at 3 pm, local police, bomb squad, dog squad were rushed to the spot, Deputy Commissioner of Police (north) M K Meena said. "Teams are checking the hospital. Nothing suspicious has been found yet." In a statement, an official at the Burari Hospital said, "At around 3 pm, we received an email regarding a bomb in the hospital. After this, all the safety measures had been thoroughly checked and everything was stable. This was the first time we received such an email." Sanjay Gandhi Hospital also received a threat email around 3 pm, according to officials.

"Soon after the call, we immediately pressed two fire engines at both the locations. Teams have been sent at all the locations from where we are getting calls. The search operation is going on," a DFS official said.

On May 1, over 150 schools in Delhi-NCR received an identical threat email claiming that explosives had been planted on their premises, triggering massive evacuations and searches. The authorities later declared it a hoax.

The Delhi Police's anti-terror unit special cell traced the domain of emails to Russia and it is suspected to have been formed with the help of the dark web -- an encrypted online content that allows individuals to hide their identity and location from others.

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