North Wales Police believe a 19-year-old man who died on Saturday had taken "a quantity of tablets", which they believe he had been sold "by an individual within the local area."
The death of Thomas Jones from Llangefni is currently being treated as "unexplained."
Police are investigating whether his death is linked to what they believe is a form of ecstasy called "Green Apples."
DCI Andrew Williams he is "absolutely desperate to ensure that nobody else loses their life as a result of taking these tablets."
Anyone with information about people who use or supply "Green Apples" or any other controlled drug is asked to contact North Wales Police on 101, or Crimestoppers on 0800 555 111.
More top news
The Children's Commissioner has found that nearly a third of five to eight year olds are left feeling hungry after a school dinner.
A cold but bright start to Friday, then a largely dry and bright day.
There are calls for dog owners to do more to control their animals after a spate of attacks on dogs in Port Talbot.