Federal government regulators in the US have warned 350 clinics that they may have received fake Botox from Canada.
The Food and Drug Administration (FDA) sent letters last month to the clinics that received the Botox from an unregulated Canadian supplier called Canada Drugs.
Canada Drugs has previously been tied to shipping unapproved and counterfeit cancer drugs to the US.
FDA officials wrote: "To minimize the chance of patients receiving an unapproved, counterfeit, unsafe, or ineffective medication, FDA requests that medical practices stop administering the unapproved versions of Botox and any other products they have received from foreign suppliers owned and operated by Canada Drugs."
The FDA has warned US doctors to not buy drugs from sources that are not licensed in the US.
CBC News reported that it is the fifth warning issued this year.
Earlier warnings were sent out regarding the cancer drug Avastin, which is made by the pharmaceutical company Roche.
The Associated Press reported that earlier in the fall, the FDA ordered 4,100 websites to stop selling unapproved medications to US consumers.
Most of the sites were created by Canada Drugs, which continues to operate.