OTTAWA -- Health Canada is advising anyone who bought a natural health product claiming to treat cancer called Novodalin B17 to contact their doctor for a followup.

The federal agency says it's an unauthorized product and that it does not permit cancer treatment claims to be made for natural health products.

Health Canada says Novodalin B17 "poses serious risks to health" because it purportedly contains apricot kernel extract.

That extract may contain amygdalin, which the agency says "has the potential to release cyanide when ingested by humans."

The Health Canada statement issued Tuesday says the concentration of amygdalin in the product is unknown, but ingesting low to moderate amounts of cyanide may lead to serious adverse health consequences and high doses may be lethal.

The agency says it has asked the online seller of the pills to stop sales and warns it will take further action.

The product was still on the online merchant's website early Wednesday, with 100 pills selling for $114.99.