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CBS – Hospitals around the country have seen a severe spike in synthetic marijuana overdoses.

The American Association of Poison Control Centers says more than 1,900 calls related to synthetic pot have been made since the start of the year. That is four times more than there were at this point last year.

Synthetic marijuana goes by many names: “Spice,” “K2,” “head trip,” “fake weed.” It’s a plant material coated with THC, the active chemical compound in marijuana. But unlike pure marijuana, the man-made version is much more potent and can be deadly.

This week in Louisiana, one person died from synthetic marijuana. Earlier this month in Mississippi, two brothers, Joey and Jeremy Stallings, were in medically induced comas after their mother said they smoked Spice.

“This stuff is no joke, and we’re really afraid because the use of it is increasing,” said Bruce Ruck with the New Jersey Poison Center at Rutgers University.

The Drug Enforcement Administration banned synthetic marijuana in 2011, but still people are finding it in places like tobacco shops and online.

From March 15 through April 20, 462 people in Alabama were sent to the ER; two of them died. In Mississippi, 473 people were hospitalized. Officials say it’s possible seven deaths were linked to synthetic marijuana.

And since April 8, it’s sickened more than 160 patients in New York.

“People have presented with seizures, people have presented with stroke-like symptoms, or heart attack-like symptoms,” said Dr. Ruben Olmedo of Mount Sinai Hospital, who has treated several cases.

Asked if he thinks people believe synthetic is safer than other forms of marijuana, Olmedo said, “They hear the word ‘marijuana,’ and they think it’s a safe drug.

In January, specialist Kendrick Vernell Sneed was found dead at home in Texas. His death triggered a brief Ebola scare because he had just returned from West Africa. But autopsy results found the 24-year-old died of synthetic marijuana intoxication.

In Oklahoma City, police say a school bus driver was high on K2 when he hit at least five cars last week. At least two other drivers were injured.

“Our warning is don’t try any of this stuff, even marijuana that you buy in the street,” said Ruck. “You do not know if it is laced with any of these synthetic products.

There are hundreds of varieties and new formulations of synthetic marijuana appearing monthly. The products often carry a “not for human consumption” label in order to disguise the true purpose of the substance.