(CNN) -- In a move that drew fire from medical marijuana advocates, federal authorities raided 26 medical marijuana dispensaries in 13 Montana cities, saying they have probable cause to believe that the businesses are involved in large-scale trafficking.
The search warrants executed Monday are the culmination of an "18-month, multiagency investigation into the drug trafficking activities of criminal enterprises," Michael Cotter, U.S. attorney for the District of Montana, said in a statement Tuesday.
In addition, he said, civil seizure warrants for financial institutions in Bozeman, Helena and Kalispell were executed, seeking up to $4 million. Authorities did not disclose items that were seized pending the filing of search warrant returns in federal court.
Probable cause exists to believe that the shops were involved in conspiring to manufacture and distribute marijuana and evade financial reporting requirements, authorities said. No criminal charges have been filed.
"When criminal networks violate federal laws, those involved will be prosecuted," Cotter said in the statement. Individuals who are in compliance with state law are not the focus of the investigation, authorities said.
Items seized included marijuana plants, computers and cell phones, CNN affiliate KULR reported. In some instances, the station said, bank accounts were frozen.
Medical marijuana advocates cried foul.
"Not only are these raids very harmful and unnecessary, they are aimed at undermining the democratic process by preventing the people and legislators of Montana from addressing their own public health concerns," Steph Sherer, executive director of Americans for Safe Access, said in a statement.
The organization describes itself on its website as "the largest national member-based organization of patients, medical professionals, scientists and concerned citizens promoting safe and legal access to cannabis for therapeutic use and research."
Sherer said, "there is no doubt the raids were times to take advantage of a vulnerable political time for Montana patients." Shere testified last week at a state Senate hearing on a bill to repeal the state's medical marijuana initiative. The measure, which passed the Montana House last month, died in committee, the organization said.
"The public has been hoodwinked into believing the feds have changed their policy with respect to medical marijuana, but the evidence points to the same aggressive tactics under President Obama that we saw for years under the Bush administration," Sherer said in the statement.
Tom Daubert, who authored the 2004 medical marijuana initiative, told the Great Falls Tribune newspaper that the raids had a "chilling effect" on the state's medical marijuana community.
Mort Reid, the owner of one dispensary, Canni-RX in Billings, told KULR he closed his doors briefly Monday after hearing of raids elsewhere because he didn't want his patients or staff to be alarmed if he was raided. He reopened later in the day but said he is still concerned a search warrant might be executed there.
Reid said he has written Montana Gov. Brian Schweitzer and said the issue is now one of states' rights.
"We still have patients to serve and I think we as a company have to put their needs above whatever motives are behind the federal authorities," Reid told KULR.