A police crackdown at a market in Don Muang district on Wednesday found that almost every shop was selling illegal goods, including cosmetics and weight loss products.

Some 400 officials from the Crime Suppression Division, Consumer Protection Police Division, Metropolitan Police Bureau, Tourist Police Bureau and the Food and Drug Administration (FDA) searched over 200 shops in Talat Mai before noon.

A large volume of food supplements and cosmetics suspected to be substandard or not registered with the FDA, was seized for inspection, said Pol Gen Wirachai Songmetta, deputy chief of the Royal Thai Police.

The operation came after authorities received many complaints saying around 200 stores were openly selling illegal products including medicine, said a source.

Among them were products branded as Magic Skin and Lyn.

Magic Skin was found to be producing cosmetics and food supplements which were both substandard and unlicensed. Lyn offered weight-loss drugs that have been linked to at least three deaths.

Despite selling contraband, the stores escaped previous crackdowns because a former police official who served as caretaker of the market abetted them, the source claimed.

Several shops were already shut by the time the officials arrived at about 11 am, while others were closing as officials approached, according to witnesses.

Pol Gen Wirachai said all of the stores would be treated equally and the authorities will quickly follow up on those that were closed.

Authorities are also investigating if the Lyn weight-loss food supplement was distributed there.

Police have obtained information confirming that an illegal factory in Thailand is manufacturing the product, he said.

The raid followed a series of crackdowns on illegal cosmetics and weight loss products.

On Sunday, police raided a factory in Pathum Thani's Klong Luang district after arresting eight suspects the same day.

The raid found stocks of Magic Skin Co products with the trademarks Apple Slim, Slim Milk, Snow Milk, Fern, Magic Skin, Shinoshi, Treechada and Mezzo. Each carried either a fake FDA certificate or the wrong certificate.

In a related development, Somchai Preechathawekij, deputy secretary-general of the FDA, said the Lyn-branded weight-loss product remains on the FDA's list of registered products pending a formal inspection.

It will take a month for the FDA's laboratory tests to reconfirm whether it contains any prohibited substances, officials said. If the results come back positive it will take one or two days for its FDA-registered label to be revoked.

Dr Wanchai Sattayawutthipong, secretary-general of the FDA, admitted that some of the Lyn product may still be in stock at some shops. He asked consumers to refrain from buying it.

The FDA and National Broadcasting and Telecommunications Commission are scheduled to announce today a joint effort to protect consumers from untrue or exaggerated product ads on TV, radio and online.