Law enforcement agencies in the U.S. are seeing a rise in the use of a potent and dangerous street drug called gravel, also known as Flakka, which can stimulate extreme paranoia and even suicidal thoughts in people who use it. A string of recent incidents in South Florida in which people high on gravel were found behaving erratically and even violently have put a spotlight on the drug in recent weeks. But police officers first began encountering gravel in 2012.

The gravel name comes from its white, crystallike appearance. The rock-like substance contains a synthetic stimulant called alpha-Pyrrolidinopentiophenone (alpha-PVP). It belongs to a class of chemicals, called cathinones, which affect the central nervous and cardiovascular systems. Gravel, or Flakka, has been compared to “bath salts,” a designer drug whose name comes from drug dealers disguising and selling it as true bath salts. Bath salts made headlines in 2012 after a Florida man who was under the influence of the drug was caught eating another man’s face.

Gravel made its debut as early as 2012 in Tennessee and Ohio. That year, it sold for $80 to $200 a gram based on its purity, law enforcement sources said. Less-pure versions of the drug have been found to contain rat poison, bath salts and methamphetamine, WBNS-TV in Columbus, Ohio, reported.

Law enforcement officials are particularly concerned about the latest iteration of the so-called insanity drug. “Gravel can potentially be even more dangerous than the synthetic drugs we were dealing with last year, mainly because you do not know for sure what other drugs have been mixed with the PVP,” Sullivan County (Tennessee) Sheriff’s Office spokeswoman Leslie Earhart told the Kingsport (Tennessee) Times-News in October 2013. “There have been reports of dealers trying to pass straight ammonia nitrate off as gravel.”

That year, police in Sullivan County encountered several instances of people high on gravel acting volatile, including a man who a man who assaulted his girlfriend because he thought she had placed surveillance equipment in all of their electrical appliances, Earhart said.

Last year, in Ohio, law enforcement agencies were told to keep a lookout for gravel after a string of arrests involved people either selling or buying the drug. A total of 670 cases involved gravel in 2014.

Most recently, the drug has been found around South Florida. The version found there comes from China, India or Pakistan and is either injected, snorted or smoked. In March, a man in Fort Lauderdale was caught trying to break into the police station by kicking the door and throwing a rock. Last week, a man high on gravel was arrested in Melbourne after he ran around naked and reportedly tried having sex with a tree.