Nitrous oxide cannisters and used balloons have been found by police in Peterborough.
While on patrol in the city centre, officers came across the items that were left in the Broadway car park behind Tesco.
NOS is now classed as a class C drug, and anyone found in possession of it may face prosecution.
Police officers spoke with the building manager who informed them that drugs paraphernalia is found in the car park almost daily.
"We will continue to visit the area whenever we can, talking to those we see about the issue," said a spokesperson for Cambridgeshire Constabulary.
"If you have any concerns around drug use and the associated anti-social behaviour, you can report it to us via our website: https://orlo.uk/dUyPy."
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