A super-sonic sound rattled denizens of this tech city, sparking wild rumours of an earthquake, an explosion or a fighter jet cruising at high speed, an official said on Wednesday.

"An inquiry has been ordered to ascertain the cause of a super-sonic sound in the city this afternoon (around 1.30 p.m.) after it set off panic and rumours of a quake or explosion due to mining blast," an official of the state Natural Disaster Management Authority (NDMA) told reporters here.

Ruling out an earthquake as the cause of the unusual sound, a Karnataka State Natural Disaster Management Committee official said seismometers did not capture any ground vibration, which occurs during a mild tremor.

"The activity is a loud unknown noise," said the official in a brief press note.

An NDMA official, however, attributed it to the like effect of a heavy vacuum caused by the sudden entry of cyclonic wind between hot and cold air, as it happened a year ago.

"The explosive sound is not because of a quake in the city and no need to panic," asserted the official.

A city fire brigade official said the massive sound could be due to mining blast of rocks for underground construction.