DULUTH — Authorities have seized 20,000 packets of suspected synthetic marijuana from a Duluth head shop as part of a nationwide crackdown.

The U.S. Drug Enforcement Administration says Wednesday’s raid on the Last Place on Earth also netted two assault rifles, three handguns and cash estimated at about $20,000.

Authorities also seized about $2.8 million from the store owner’s bank accounts and two vehicles.

Three customers were arrested on outstanding warrants not related to the investigation.

Close to two dozen officers participated. Police also raided the Last Place on Earth last September.