Hundreds of people across East Lancashire reported hearing a loud "booming" noise in the early hours of this morning.
Social media was flooded with comments about the mystery sound that several people heard in the the Ribble Valley but also in Hapton and Colne.
Many said the sound was so strong it rattled the windows of their homes while one person commented on the Clitheroe Buy and Sell facebook page that he heard the noise in the Gargrave area and seconds after a jet flew over.
One explanation given for the noise was that it was an RAF Typhoon jet which are only allowed to fly supersonic if responding to an emergency.
Similar explosion sounds have been reported across various parts of the world.
In November this year a similar sound was heard in the Merseyside area which turned out to be thunder.
But the source of many of the sounds remains unsolved with several theories ranging from fighter jets to mini meteors colliding with the earth.