The medicines regulator is warning people against using two weight loss products, because they contain prescription drugs.
Medsafe said people who have been taking Go Lean Detox and Go Detox should stop and return the products to the supplier or dispose of them safely.
The products have been tested by ESR and the prescription medicines they contain - sibutramine and phenolphthalein - haven't been declared on the label.
Medicines containing sibutramine were previously marketed in New Zealand for weight loss, but they were withdrawn from the market here, and other markets internationally, in 2010 following a review of a study that found an increased risk of heart attacks and strokes associated with this medicine.
Phenolphthalein has a known laxative effect and is no longer used in medicines in New Zealand.
Medsafe said they have had a report of one person experiencing side effects after taking one of the products.
But it said there was no reliable information about how many people had taken these products.
Medsafe has notified the known distributors of the products, which are thought to have been sourced through Vietnam, to immediately stop supplying them.
Stocks of the products have been seized.