Hundreds of Scots were rudely awoken in the middle of the night by a bizarre boat horn blasting from the River Clyde.
Scores of residents in the Clydebank and Erskine area took to social media in a bid to discover what was causing the racket shortly after midnight.
Many joked that they feared it was the real-life beginning of the hit thriller movie the Purge.
Other suggestions included alien invasions, a meltdown at Faslane Naval Base in Helensburgh or the end of the world.
One person wrote: “Literally thought aliens were beaming down on us last night, never heard anything like it.
“How loud was that, even considered it being a nuclear mishap signal or something from Faslane.”
Another posted: “That boat horn was f****** terrifying. A thought the rapture was finally happening.”
A third said: “I’m guessing that horn was a boat on Clydeside in Clydebank and not the start of the purge.”
Greens MSP Ross Greer shared a video of the strange siren and joked that it was like a horror movie.
He tweeted: “If this is Silent Hill it's pretty s*** so far. If we've been nuked and I'm in heaven, also underwhelming because my shower's still broken.”
Greenock Coastguard and Rescue Team allayed any fears however by revealing it was a malfunctioning distress system on a ship.
They said: “We can confirm that a vessel in the Clydebank/Erskine area had a malfunctioning distress system resulting in distress horns being activated around 00:30.
“Our operations centre have spoken with the vessel in question and can confirm she is safely alongside and in no distress, there is no requirement to report this to us.”
