Police are warning the public to be aware of chalk marks being left on their homes.
Officers believe the marks may have been made by potential burglars as two homes marked had expensive bikes in the garage.
A spokesman for Burnley Police said: “We have had reports of people finding chalk marks on their properties.
“It was established the properties that had been marked both owned expensive bikes that were in their garages.
“We are concerned that the marks are put there to identify properties to be targeted later.
“If you notice any chalk marks on gates, doors or on the path, please let us know. There may be other similar things happening which may not involve bikes so please, if you do see chalk marks, don’t ignore them.”
Anyone with information can call police on 101 or Crimestoppers, in confidence, on 0800 555 111.