Colorado police are warning parents that sweets laced with marijuana may end up in children's Halloween trick-or-treat bags.
The state was the first in the US to allowed recreational sales of the drug to adults earlier this year.
Experts issued pictures of two nearly identical gummy bears - one infused with marijuana concentrate and one without - and said it was almost impossible to tell the difference.
Police have also released a video warning parents some sweets may not be all they seem and they should check the products are made by well-known brands, throwing out anything that appeared tampered with.
Police say it is very hard to tell the marijuana sweets from regular candy
Sergeant Brett Hinkle from Denver police's marijuana unit said: "Apples, gummy bears, there's a ton of different edible stuff out there on the market that's infused with marijuana."
Anti-drug activists say kids' favourites such as Sour Patch Kids, Pixy Stix and peanut butter cups have all been found in Colorado infused with potent marijuana concentrate.
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