Two products sold on e-commerce platforms as weight-loss supplements have been found to contain harmful substances.

The products - Serifa Beauty Solidmolid and LKS Coffee - both contain sibutramine, a banned substance that could increase the risk of heart attack and stroke, and cause insomnia and hallucinations.

The Health Sciences Authority (HSA) said in a statement yesterday that LKS Coffee and Serifa Beauty Solidmolid were sold on Shopee and Carousell, as well as on social media websites Facebook and Instagram.

Both products had been marketed as slimming products containing natural ingredients.

Serifa Beauty Solidmolid was marketed as being able to "burn fats up to 10X", while LKS Coffee claimed to be able to "accelerate fat burning", "promote metabolism" and "achieve the perfect slimming effect".

However, a consumer who took Serifa Beauty Solidmolid experienced rapid heartbeats, while those who took LKS Coffee reported sudden weight loss and loss of appetite.

The HSA's tests revealed that both products contained high levels of sibutramine.

The authority has issued warnings to the sellers and directed the website administrators to take down the listings.

The public should stop taking these products immediately and see a doctor if they feel unwell, said the HSA.

It also warned sellers and suppliers to stop selling these products immediately.

Those who are convicted of doing so face a fine of up to $10,000 or jail of up to two years, or both.