GREEN BAY, WI (WTAQ) - A smoke shop in downtown Green Bay is closed, after authorities bust the owner for selling synthetic marijuana. 

Green Bay Police say the investigation began back in July, after arresting a man for possession of synthetic marijuana. 

On Monday, police along with the Brown County Drug Task Force executed a search warrant at Imports Plus on South Broadway. 

They seized three truckloads of synthetic marijuana, drug paraphernalia and cash worth tens of thousands of dollars. 

The owner, Michael Denis and an employee, Amy Richards were arrested. 

Synthetic marijuana, known by names like K2 or Spice, were made illegal by the state legislature last year. 

Police says customers would use a codeword to buy it from behind the counter. 

Imports Plus is now closed. 

The investigation continues, and no formal charges have been filed yet.