(CNN) -- More than 150 people were arrested in a four-month nationwide roundup of alleged sellers and makers of synthetic drugs, substances that authorities say can be more dangerous than the drugs they mimic, the U.S. Drug Enforcement Administration said Wednesday.
Federal, state and local agencies collaborated on the arrests, targeting drugs such as synthetic marijuana -- often sold online and labeled as incense to hide its purpose -- and hallucinogens and stimulants sold under the guise of "bath salts" or "plant food," the DEA said.
Authorities seized hundreds of thousands of synthetic drug packages and more than $20 million in cash and assets in the 29-state, January-to-May roundup, which the DEA said was the second phase of an operation called Project Synergy.
"Many who manufacture, distribute and sell these dangerous synthetic drugs found out first hand today that DEA will target, find and prosecute those who have committed these crimes," DEA Administrator Michele Leonhart said, adding the agency was targeting those "who are all too willing to experiment on our children and young adults."
Synthetic drugs are a wide range of chemical products with ever-changing -- and often dangerous -- ingredients. Synthetic marijuana, for example, can be plant material treated with psychoactive compounds that mimic marijuana's active ingredient.
Authorities and researchers have said synthetic drugs are particularly dangerous because their ingredients can be particularly potent and haven't been tested for safety. Users of bath salts sometimes have violent episodes, extreme paranoia and disorientation, the DEA says.
In the roundup's first phase, authorities arrested more than 227 people from December 2012 to June 2013, the DEA said.
An Iowa City shop was among those busted May 7, according to KCRG.