DENVER – Fears that trick-or-treaters here might end up with marijuana-laced candy on Halloween appear to have been overblown: Children's Hospital Colorado reported no instances of accidental pot poisonings from Friday night.

The Denver Police Department last month warned parents to be on the lookout for marijuana candies, in large part because they are virtually identical in appearance to candies available from grocery stores. And some "edibles" makers simply buy commercially available candies and spray or inject them with marijuana oil.

While edibles have been available for years under Colorado's medical marijuana system, the Jan. 1 legalization of recreational sales has spurred an explosion in their consumption. Some stores report that 40% of their sales come from edibles, with the rest from marijuana flower or "bud," hash and other THC-containing products.

Before Halloween, the marijuana industry scoffed at parents' fears and said the vast majority of users are responsible adults who would never actually...