The police control room received a call from an unidentified mobile number around 8.40 PM about a bomb planted inside the Delhi Police's headquarters at ITO.
Initially, the police believed that the call was made from an Aircel number, but later on it was found to have been ported out to Vodafone, a senior police officer said.
Vodafone, however, informed that the number has been inactive since December 18 last year, he said.
A bomb disposal squad inspected the building but no suspicious items were found, sources said.
The police are investigating the matter.
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