Initially, the rumour had it that the sound could have been triggered due to "sonic boom" created by some military aircraft.
On being contacted, Defence spokesman Col SD Goswami, denied that it was an explosion, and said as far as the Air Force is concerned, they are trying to ascertain the facts.
Sonic boom is created by objects travelling at speeds faster than the speed of sound. They generate enormous amounts of sound energy, much like an explosion.
As per the regulations, no sonic boom should occur in populated areas.
