Montreal - Hudson and St-Lazare were rocked briefly by the sound of an explosion around 8 p.m. Tuesday, but the source of the big boom remains a mystery.

Officials in the off-island towns, as well as the Surêté du Québec, were flummoxed, leaving residents who heard the noise to wonder on Twitter what happened.

"No one seems to know what it is exactly but a friend described it as a bright blue flash in the sky followed by the sound," wrote Kalina Laframboise.

"It's been heard all over the region but no details," wrote Greg Patterson. "My opinion is that it was a meteor hitting the atmosphere with sonic boom."

Did you hear anything?