People across Lancashire are reporting the sudden appearance of mysterious marks on their homes and driveways.
Some people are concerned that the sinister symbols found painted on pavements, fences and walls are a sign that their home has been targeted by burglars.
Others speculate that the chalky white lines are used by dog snatchers to identify the homes of valuable pets.
But do the mysterious marks really mean that your hound and home are on a hit list?
Susan, from Carleton, found chalk marks outside her home on Thursday December 3.
A white X mark had appeared overnight on the front of her home. She also found other strange markings on pavements and lamp posts in the area.
When she raised her concerns with neighbours, she was told about the 'Da Pinchi Code' - an apparently secret set of symbols used by criminals to identify vulnerable homes.
Susan, who lives on the Arundel estate, was so afraid that she reported the markings to police.
She said: "My house has a public footpath running along the side of it and today, when I was walking my dog, I noticed that white chalk circles have deliberately been put on the fence posts bordering my garden.
"There's another one that has been put on the street light outside my house. That one has a cross through it. But what worries me most is the X near my front door.
"I know there has been criminal activity around Carleton recently, with a lot of houses and shops broken into.
"I am anxious as I have read that these marks can have a lot of distressing outcomes and could be the handiwork of burglars."
Responding to her appeal for help online, Susan's neighbours revealed they too had found the marks appearing on brick paving, walls and gate posts.
Michelle Harvey, from Carleton, said: "We had our house marked by chalk twice in the space of about three weeks a couple months back.
"Markings can be used as messages for targeting properties or it could be innocent. I advise washing them off as soon as possible."
Laura Heaton added: "I heard that people circle in white chalk if you have a dog. They come back later on to steal the dog"
The marks are playfully known in some areas as the 'Da Pinchi Code'.
Da Pinchi decoded - Is there a secret set of symbols used by criminals?
The Da Pinchi Code is allegedly a series of symbols painted or scratched into surfaces near homes. Some people claim that the secret code is used by criminals to identify homes occupied by vulnerable people, or homes that are considered desirable targets.
What do the marks mean?
For those who believe in the Da Pinchi Code, each mark has its own meaning.
- Two squares: Elderly and afraid occupants
- Crosses or X shapes: High value target
- D shapes: Too risky
- Upside down pyramid: Alarmed house
- Open book shape: Vulnerable female
- Circle: Lone occupant
- Circle with a cross through it: Nothing worth stealing
- Square with circle inside: Already burgled.
Could there be a more innocent explanation?
Other people believe they have cracked the code and claim the markings are not the sinister symbols that some homeowners fear.
According to sceptics, the true meaning of the chalk marks is much more innocent.
Mark Walters, a builder from Poulton-le-Fylde, said: "The signs indicate work planned by utility firms. They are used by engineers to mark locations where kerbs and water pipes need repairing.
"Also, if you find them on exterior brickwork, they can be caused by efflorescence."
Efflorescence is a type of white deposit found on masonry. It's formed when water reacts with the natural salts contained within construction material and mortar.
Mark added: "The water dissolves the salts which are then carried out and deposited onto the surface by the natural evaporation that occurs when air comes into contact with the surface of the wall or floor."
What do the police say?
In recent years, some police forces in Britain have taken to social media to warn people about the markings.
In 2016, Lanarkshire Police shared some of the symbols on social media and said it could be a 'housebreakers code'.
Police in Devon also suggested this was the case in 2013 and even advised homeowners to learn the code to help protect their property.
But according to Lancashire Police, there is no evidence that the white marks are cryptic messages used by criminals.
A spokesman for Lancashire Police said: "Chalk markings outside properties is something which has cropped up from time to time throughout the country and there have been a number of theories about who is responsible, including utility services (gas/water), children and even running clubs marking out a route.
"We have no evidence at this time to suggest that the drawings you refer to are linked to any organised criminal activity.
"We would, of course, advise anyone who has concerns or information about criminal activity in their community to contact their local neighbourhood policing team."