More than 50 people have been treated after apparently taking the synthetic marijuana drug K2 in the Austin, Texas area, authorities said.
Earlier Thursday, Austin police had said around 20 patients downtown were treated for suspected reactions to the synthetic drug — which can cause elevated heart rate, seizures, hallucinations and has been linked to deaths — in medical calls downtown that began at around noon
The Austin-Travis County EMS said later on Twitter that over the last 24 hours it responded to 45 K2 cases involving 52 patients.
"It’s dangerous," Austin police Lt. Kurt Thomas said at a news conference. "It will hurt you as we’ve seen today — people are having all kinds of distress and having to go to the hospital."
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Three people suspected of being involved in distributing the synthetic marijuana downtown were taken into custody and were being questioned, Thomas said.
The type of drug is often manufactured in China and shipped to the U.S., authorities say. Synthetic cannabinoids had been sold in smoke shops and convenience stores, but the Drug Enforcement Administration listed some types of the drug and substances used in them as a controlled substances in 2011, and federal law expanded bans.
Related: Everything You Need to Know About K2, Drug Linked to Mass NYC Overdose
The DEA found twenty deaths between 2011 and 2015 linked to synthetic cannabinoids, according to a July report by the Centers for Disease Control and Prevention. The class of drugs includes K2 and "spice," but recipes frequently change.
In Los Angeles, police suspect a bad batch of the synthetic drug "spice" sickened 50 people in the Skid Row area on Aug. 19 and another 14 on Monday, NBC Los Angeles reported.
In Brooklyn, New York in July, 33 people were hospitalized after authorities responded to calls of K2 overdoses at an intersection. Neighbors told NBC New York drug users in the area smoke K2 and "drop like flies."
Synthetic cannabinoids were first synthetized in the 1960s and began appearing on the Internet and in smoke shops in Western Europe in 2004, according to the CDC. The first seizure of the substance in the U.S. was in 2008.
After a spike in reported synthetic cannabinoid poisoning cases in 2011 of around 6,900 cases, the numbers dropped until 2015, when 7,779 cases were reported, according to theAmerican Association of Poison Control Centers.
There have been 1,682 reported poisoning cases in 2016 as of July 31, according to preliminary numbers from the association.