Officers from the Duluth Police Department stand outside the Last Place on Earth Wednesday afternoon in Duluth, Minn. The head shop in downtown Duluth was shut down Wednesday as federal agents and local law enforcement executed a search warrant as part of an ongoing investigation. Derek Montgomery for MPR

Federal and local law enforcement officers raided a shop that sells synthetic marijuana in Duluth Wednesday afternoon.

The Last Place on Earth is a head shop owned by Jim Carlson. He's fought both a city and state law banning synthetic drugs, some of which is sold in packages labeled as "incense."

Jeanne Cooney, spokesperson for the U.S. Attorney's office said the raid was part of a "broader investigation." It included Duluth police, members of the Lake Superior Drug and Gang Task Force and Drug Enforcement Administration (DEA) agents.

"Our interest in the business today is that we want to serve some search warrants there," Cooney said.

Two people in the store were arrested for outstanding warrants, although the arrests weren't related to the search warrants, Cooney said.

The state Legislature tightened its ban on synthetic drugs last session. President Barack Obama also signed federal legislation banning synthetic drugs earlier this month.

The shop was previously raided in September 2011 and synthetic drugs were seized, although no arrests were made then.