As the source of manufacture has not been approved, the food safety of the product is in question, said the agency.
The CFS called on the public not to buy the product concerned if it is found on sale in retail outlets and trade should stop selling the product as it may violate the law.
"Following up a complaint, the CFS found that the milk product concerned in paper pack (1 litre) was placed on the shelf in a grocery store at Wang Fat Path in Yuen Long,” the spokesman said.
“Source tracing of the product concerned is in progress and the trade will be alerted of the incident. The CFS will consider taking out prosecution action based on the investigation result.”
The maximum penalty is a fine of $10,000 and imprisonment for three months.