Fake police notices have been stuck on cars in Bicester by someone claiming to be cracking down on bad parking.
And some vehicles in the same area have had their tyres slashed - but police so not know if the two incidents are linked.
Thames Valley Police said they are aware of the notices placed on cars in the Kingsmere estate.
"It probably will come as no surprise to our followers to learn that this particular notice was not issued by police (and we certainly don't use glue when placing advisory notes on vehicles)," said a spokesperson for Thames Valley Police.
"However, we are investigating a series of criminal damage offences on the Kingsmere estate, where the tyres of several vehicles have been found slashed.
"In all cases, the vehicles were legally parked, either on the roadway outside of the owner’s home address, in a visitor’s bay or even on their own driveway.
"We are also aware that some residents may have experienced similar incidents with their own vehicles but have not yet reported them to police.
"If this is the case, we urge you to do so, either by phoning 101 or by reporting online at https://tinyurl.com/4zuathz5."