Two people have been arrested following spot checks by police at Anglesey's pubs and cars.
Officers visited licensed venues across the island to check for signs of drug use in the run up to Christmas.
Several people were stopped and searched when a specially trained dog indicated the presence of drugs.
Two arrests were made for possessing suspected class A drugs - and further traces were found in a number of premises visited by police.
Two more people were arrested on suspicion of drunk and disorderly behaviour and were referred to Checkpoint, a voluntary programme for offenders which aims to prevent further disorderly behaviour.
North Wales Police said they were working with licensed venues to tackle drug use.
Neighbourhood Policing Sergeant Dylan Roberts said: "I am grateful to the local licensees for their ongoing support and continue to work with them to ensure a safe nighttime environment for the residents of Anglesey."
"It is concerning to find traces of suspected class A drugs in some of the premises and we are committed to working with partners to eradicate this."
"We will soon be returning to more pubs across Anglesey with the assistance of the drugs dog to carry out more checks during this busy period."
"I would encourage anyone with concerns about drug use in their local area to report it to police or anonymously via Crimestoppers."
Anyone with information should contact North Wales Police on 101 or Crimestoppers anonymously on 0800 555 111.