The cause of a strange humming sound heard around Strangford Lough, which has left locals baffled, is still being debated.
Belfast Telegraph readers have been trying to figure out what was behind the noise since it was first reported by this newspaper last week.
The mysterious sound, which lasted for more than three hours, was heard from around midnight on Friday, November 8.
Ian McConnell was among those left puzzled as to the cause.
He captured a video with the peculiar humming sound to share on social media and the noise - which sounds like a loud car horn going off - can be heard clearly.
The 52-year-old writer, who lives in Kilclief, three miles from Strangford, could only hear the hum from outside his house.
Readers have been taking to social media to try and solve the mystery for themselves.
From 5G to cars, Stephen Nolan and Brexit - the suggestions have been varied.
One reader contacted this newspaper over the weekend with his theory that a dead seal on the shores of the lough was the cause.
"I think this very badly injured seal may have been the cause of the humming noise on the lough," he wrote, complete with a photo of the dead seal.
But Mr McConnell said the sound was more "like a droning or a hum" and he is still baffled.
"I was sent a message on Twitter from someone who suggested that it might be the Strangford bar mouth whistling buoy.
"It's been there for a century, so I'm not sure that would be it.
"I remember hearing something similar on a crossing from the Isle of Man on a windy day.
"What I heard wasn't whistling but I'd say that would be quite eerie to hear on a sea crossing," he said.
Did you hear the strange hum in Strangford recently or do you know what it was?
If so, contact newseditor@ belfasttelegraph.co.uk