DENVER – A town south of Denver has banned the sale of the herbal supplement kratom to anyone under the age of 18.

The Denver Post reports the Castle Rock town council approved an ordinance Tuesday that imposes a $300 fine on anyone caught selling the substance to minors. The town late last year imposed a six-month moratorium on the licensing of any new kratom shops while new rules were established.

Kratom, which is derived from the leaves of a tree that grows in southeast Asia, often is used in the form of an extract or a pill. Many see it as a safe, natural alternative to opioid painkillers. But the Food and Drug Administration says it exposes users to the risks of addiction, abuse and dependence.