Police are warning Brooklyn residents about a dangerous dose of the synthetic drug K2 circulating in the borough. 

Investigators say the drug was purchased at five locations, including in Bedford-Stuyveant and East New York.

Police have 56 confirmed K2 overdoses in Brooklyn so far.

The Health Department says 84 people were rushed to the emergency room after ingesting the drug between May 19 and May 21.

More than a dozen people have been arrested.

The latest was Jasmine Alicea, who's being charged with the sale and criminal possession of a controlled substance. 

"We've made the arrests in the areas. We're debriefing individuals, and we want to identify the source and work on the major cases," said NYPD Chief of Department Terence Monahan.

"The chemical balances and how it's manufactured are very dangerous, when you see some of the results and people foaming at the mouth, things of this nature, but this particular batch is really concentrated. It's in a confined area," said NYPD Chief of Detectives Dermot Shea. "We don't normally see individuals passing out, going to the hospital in these great numbers."

K2 is a form of synthetic cannabis. It has been banned in the city since 2015.