Some medical marijuana shops in central California have closed down following a letter from federal prosecutors threatening their landlords with legal action.

The Associated Press reports many of the 38 clinics in central California, from Santa Barbara to San Bernadino counties, have closed because landlords were given two weeks to evict them. Four U.S. attorneys said they would prosecute landlords who rent space to operators of medical marijuana dispensaries. The landlords were threatened with criminal charges or seizure of their assets.

The attorneys said they suspect these dispensaries of using the state’s medical marijuana law to profit from large-scale drug sales. They said they are also focusing on properties used to grow marijuana.

“What we are seeing is a wholesale violation of both federal and state law by some people involved in the industry,” Thom Mrozek, a spokesman with the U.S. attorney’s office in Los Angeles, told the AP. “There are huge amounts of money going into this industry. It’s our position that this goes way beyond simply paying rent and cultivating marijuana.”

In July, the U.S. Justice Department announced that medical marijuana dispensaries and licensed growers located in states with medical marijuana laws are not immune from prosecution for violation of federal drug and money-laundering laws.

Deputy Attorney General James Cole wrote a policy memo to federal prosecutors that states, “Persons who are in the business of cultivating, selling or distributing marijuana, and those who knowingly facilitate such activities, are in violation of the Controlled Substances Act, regardless of state law.”