Aussies are being urged to contact police if they notice "suspicious markings at their property" after one homeowner alerted others of a seemingly alarming find.
An Adelaide resident raised concerns after spotting unusual codes written on parts of their home including their fence, downpipe and the back entry to their home, and wondered if it could be related to a crime.
"Found these marked on our fence and back door entrance," the homeowner shared on Reddit, alongside photos of the marks in question.
"They appeared overnight. Thoughts? Could the house be marked for a burglary?"
Some images show "four strike marks" drawn on the fence and gutter while "NT" had been scribbled on the resident's letterbox.
The homeowner said they looked around the neighbourhood and noticed "both corner houses of our block have had their mailboxes marked," but with a different marking, an 'S'.
"I did become paranoid after we found the markings at the start and end of the street," they said, adding the quickly phoned the police.
Sinister theory emerges
People were quick to weigh in on what they thought the marks could mean, with many concluding it was the work of would-be thieves in the area.
"Peeps looking to break into your property – NT = no threat, S = security. The marks are usually the numbers of days they’ve been watching your place/how many times you use an entrance in a day," one suggested.
Another agreed saying "No Threat, from dogs or security etc," while some urged the homeowner to increase security around their home.
"My house was tagged in Melbourne and the neighbourhood FB group figured out it was all the houses with dogs and I have a bull terrier. Be careful!" one warned. But the original poster explained they had no pets.
Some were a little more sceptical and suggested that thieves "wouldn't be that stupid".
"This makes no sense, why would they alert potential victims when they could easily make notes in the phone, in a notebook, on a post-it … on the back of their hand etc etc etc," one wrote.
"It could be just kids mucking about," said another.
Police respond to 'suspicious' markings
The homeowner who posted the pictures made a report to police.
"They took the report only, and said if there’s something, someone may be back in contact at a later date," they said.
While SA Police couldn't confirm what the markings were, a spokesperson told Yahoo News Australia people with these or something similar should come forward.
"If this has occurred we would encourage anyone who finds suspicious markings at their property, or notices anyone acting suspiciously in the area, to contact police and report the matter," they said.
"Police would then be able to conduct an investigation and ascertain the purpose behind the markings."
There's been a long-standing theory about thieves marking houses, prompting concerns in Australia and overseas.
In 2019, a Cairns local became concerned about red markings in the suburb of Mooroobool, believing it was the work of criminals.
Last year, a strange scribble on a NSW woman’s doorbell left her frightened her house had been targeted by thieves.
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