Florida police are grappling with a toxic designer drug that causes extreme paranoia in users, including a fear of being chased and killed or hunted by dogs, the Associated Press has learned.

Other "flakka" users tried having sex with trees and attempted breaking into the Fort Lauderdale Police Department. The Florida Department of Law Enforcement is seeing more and more cases each year all over the state- there were 228 cases in 2014, up from just 38 in 2013.

But police face difficulty controlling the substance because it's hard to trace and the manufacturers are elusive.

"It's definitely something we are watching. It's an emerging drug," Chad Brown, supervisory special agent of the Florida Department of Law Enforcement, told the AP.

Flakka, also known as gravel, gets its name from the Spanish term for an attractive, skinny woman. Made primarily in China and Pakistan, flakka is usually sold in crystal form and can be smoked, snorted, swallowed or injected.

"I've had one addict describe it as $5 insanity," Don Maines, a drug treatment counselor with the Broward Sheriff's Office in Fort Lauderdale, told the AP. "They still want to try it because it's so cheap. It gives them heightened awareness. They feel stronger and more sensitive to touch. But then the paranoia sets in."

The active ingredient in flakka is alpha-PVP, a chemical compound on the U.S. Drug Enforcement Administration's list of controlled substances with a high abuse rate. But experts have a hard time pinning down its chemical makeup because the manufacturers often change its composition and mix it with other drugs like heroine, the AP reported.

Symptoms are also hard to detect but most flakka incidents involve hallucinations and an extreme fear of being chased.

One man tried fornicating with a tree after running through a Florida neighborhood wearing nothing but his birthday suit. He later told police he was convinced he was Thor, the Norse god of thunder. Another man ran naked down a city street from an invisible pack of German shepherds.

In March, a 37-year-old man Shanard Neely accidentally impaled himself on the fence outside the Fort Lauderdale Police Department during a break-in attempt. He told police he was being chased and "needed to go to jail or they would kill him," the AP reported. Neely also admitted to smoking flakka.

Florida prosecutors are cracking down on flakka distributors, including a 22-year-old woman named Jaime Lewis accused of having packages of flakka delivered to her home. An undercover operation traced the drug from Hong Kong to London and then to her home in Palm Beach County.

Her lawyer said prosecutors will have to prove she knew the packages contained the drug, the AP reported. Lewis is expected to enter a plea next week.