Health officials in New York City are raising the alarm about smoking synthetic marijuana. According to the New York City Department of Health and Mental Hygiene, 15 people went to the emergency room over the weekend after smoking fake weed. 

That's because it's stronger than regular marijuana — hundreds to thousands of times stronger, according to New York University-Tisch Hospital's Dr. Stephen Ross. It can lead to seizures and kidney failure and can intensify the symptoms of mental illnesses. It's been illegal in new York City since 2012, but according to Ross, hospitalizations from the drug aren't stopping.

"If anything, it seems we're seeing more people in the psychiatric ERs with pretty serious psychological complications from smoking synthetic cannabinoids," Ross said.

The Health Department said that so far this year there has been a 220 percent increase in hospitalizations from severe reactions to fake marijuana. Officials are asking people to call 311 if they see synthetic weed for sale.