SAMUT PRAKAN: A seller of popular weight loss drugs under the brand name "Lyn" has been charged with selling products that contain dangerous chemicals and are believed to have killed four customers.

The arrest of Chirayut Khongwatthanukun at his house in Bang Phli district on Sunday is the latest in a string of crackdowns on cosmetics and food supplements - most recently Marry Peaw and Magic Skin - which authorities say are are unlicensed and substandard.

A police search of the premises found a large amount of Lyn products packed in black and white boxes he had bought for sale.

An inspection found detox medicines in the black boxes and diet pills in the white ones, labeled "Block and Burn."

Deputy national police chief Wirachai Songmetta, who led Sunday's operation, earlier warned people against buying Lyn products after Chon Buri health officials found they contain Bisacodyl and Sibutramine, which are listed as dangerous substances and have been banned since 1977, Naewna Newspaper reported.   

Sibutramine is an appetite suppressant while Bisadodyl is a type of laxative. They both can cause severe side effects, especially on the heart and blood veins.

An initial investigation found that four customers who used the products had died since early March.

Mr Chirayut said he sold the drugs on the Internet after he had tried them and found that they helped him lose weight. He said he did not know they were harmful to health.

The 45-year-old told police he bought 500 Lyn products from a "sales agent" and had sold them to 350 customers.

According to investigators the supplier was Phimphat Ekakkharin, who runs Ekakkharin Co.

Rangsan Wongunnak, a Samut Prakan public health official, said officials also found the product labels carry exaggerated claims.

Another food supplement, Marry Peaw, has recently been blacklisted after the Food and Drug Administration found the owner made them without FDA licences.

The scale of the scandal continues to grow as police question dozens celebrities hired to advertise cosmetics and food supplements under the Magic Skin brand.