Muriel Bowser, the mayor of Washington, D.C., posted an "EMERGENCY ALERT" on Friday warning about a "potentially fatal batch of K2" that she says has hit the city's streets. She tweeted the alert, which warns people to avoid K2, or "Spice," at all costs.
The alert, from various government agencies, also urges people say something if they see something.
The Centers for Disease Control and Prevention says K2 is a term for synthetic cannabinoids -- "synthetic marijuana" -- and that some people may use it as an alternative to marijuana.
"These seemingly innocent little packages of 'fake weed' can cause serious side effects that are very different from those of marijuana," the CDC says.
"Synthetic cannabinoid products can be toxic. As a result, people who smoke these products can react with rapid heart rate, vomiting, agitation, confusion, and hallucinations. Some have to get help from emergency medical services or in hospital emergency departments or intensive care units," it says.
In May, there were overrelated to illegal sales of K2. More than 25 people in the area were hospitalized with bad reactions to the synthetic marijuana.