Underground labs in China are pumping out massive quantities of a dangerous drug and the CDC is 'concerned'

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Spice, also known as K2, black mamba, or crazy clown, is a lab-produced, mind-altering drug that's soared in popularity in recent years.

Giant underground labs, many in China, are churning out thousands of pounds of the stuff.

The CDC announced on June 11 that as of May 2015, US poison centers received more than 3,500 calls related to use of the drug, up nearly 229% from a year ago.

While marketed as a "safer alternative" to marijuana, spice is dangerous and can be deadly.