New York, United States |"Zero percent marijuana, 100 percent dangerous." 

New York has launched a public awareness campaign in its war against synthetic cannabis, a potentially deadly drug which experts say preys on the poorest and the mentally ill.

The drug widely known as K2 has killed at least two people in recent months and sent more than 6,000 people to the emergency room in the city since January. Most were men.

It first came to the attention of authorities last year and is sold under a string of other names: Spice, AK-47, Bizarro, Green Giant and Smacked -- to name the most common.

Sometimes packaged as "aromatherapy" or "pot pourri," some bags are decorated with cartoon characters. It can be bought on the Internet but also from cigarette sellers and bodegas.

Some users wrongly think it is legal, or at least not illegal. 

But the law is clear: It is illegal in New York State to possess, sell, offer to sell or manufacture synthetic cannabinoids.

"It is very important that people understand this is zero percent marijuana and 100 percent dangerous," New York City Health Commissioner Mary Bassett told AFP.

The chemical make-up of synthetic cannabinoids, which often sell for just $5 for a bag of several grams, varies from batch to batch, with unpredictable side effects.

Bassett this week attended a gathering of 200 health professionals, magistrates, law enforcement officers, anti-drug workers and social services in New York to clamp down on it.

A public information campaign is running in bus shelters, phone kiosks, in the lobbies of homeless shelters and other places in neighborhoods most affected to warn against K2.

China is the principal source of the basic component used to create the drug, which is blended with solvents into a liquid sprayed on leaves and then sold in small bags of grass.

"K2 is a terrifying and unpredictable drug," said Julie Menin, commissioner of the department of consumer affairs.

She says users, encouraged to think that the little bags of grass are legal, never image it is a chemical construction nor what the effects might be.

"False marketing misleadingly portrays these products as safe and legal, which violates the city's consumer protection law," she said.

- Stepped-up punishments -Authorities are mailing postcards to more than 9,000 cigarette sellers, delis and grocery stores, advising them it is illegal to sell the drug and that there are penalties for those who do.

Last month, New York Mayor Bill de Blasio declared increased punishments for sellers and distributors, who face a year in jail, fines of up to $100,000 and the closure of their shop.

On September 16, authorities announced a large swoop on the K2 distribution network. Six people were arrested and 10 charged.

Most users, Bassett says, live in poor neighborhoods and those suffering from mental illness have been over-represented among those seen in emergency department visits.

Ninety-nine percent of those admitted to hospital for K2 are 18 or older, and 90 percent are men. 

The problem was first identified in New York's neighborhood of East Harlem, before spreading to surrounding areas.

K2 can cause hallucinations, anxiety, aggressive behavior, lethargy, vomiting, a loss of consciousness, convulsions and can even prove fatal. 

Deirdre Canaday, a mother of four, lost her son to K2 four years ago and knows that authorities have a reason to be very worried.

Aaron was 26 and in the prime of his life. He dabbled in the drug with his friends "to have a little fun," she told AFP.

"It was legal at the time. He only experimented half a dozen times. In the morning they all woke up and Aaron did not."

"It keeps morphing. The stuff that took my son's life was mild compared with what is out there right now," she said.

K2 is "more and more deadly, more and more unpredictable, more and more potent," she added. "It is affecting everyone."