The Food and Drug Administration (FDA) said the drugs - which are related to so-called date rape drugs - are dangerous and advised people not to take them.

The FDA said products containing the drugs were widely available.

"These products are listed as 'party drugs' on Internet sites, advertised in muscle-building magazines, and sold in health food stores as dietary supplements to aid in sleep," it said.

"The FDA, however, considers these products unapproved new drugs and has conducted seizures of the product to prevent the sale to consumers and any further illnesses or deaths."

Health risks

The agency said three drugs - gamma butyrolactone (GBL) gamma hydroxzybutyric acid (GHB) and 1,4 butanediol (BD) - had been "associated with reports of at least 122 adverse health effects, including the three deaths".

"In particular, one of these products, 1,4 butanediol (BD) has been declared a Class I Health Hazard - a potentially life-threatening risk - by the FDA," it said.

"BD is a chemical that can cause dangerously low respiratory rates, unconsciousness, vomiting, seizures and death. BD may also increase the effects of alcohol and is even more dangerous when consumed with other depressant drugs."

GHB is also known as liquid X or g-juice, and was once sold in health food stores to bodybuilders. It was pulled off the market in 1990 because of its bad side effects.

Along with another drug - Rohypnol - GHB has been associated with several date rape cases.

Drug causes confusion

The effects of GHB are similar to those of Rohypnol - dizziness, confusion and memory loss.

Instructions on how to make the drug are available on the Internet, and in January the FDA urged Congress to impose harsher restrictions on it.

But campaigners say the drug is safe and effective, both for treating sleep disorders and as a recreational drug.

They say the FDA and the US Drugs Enforcement Agency are trying to mislead the public on the drug's benefits.

GBL is not illegal, but drug agencies would like to see it outlawed. Drug companies are resisting any such move as they want to investigate the compounds' medicinal properties.

Chiropractor jailed for distributing drug

In February last year a Los Angeles chiropractor was fined $2,000 and jailed for illegally distributing drinks containing BD at a New Year's Eve 1996 party, the FDA said.

The drinks were blamed for making more than 100 party-goers ill.