The Canadian Food Inspection Agency (CFIA) is warning Canadians not to plant any packages of unsolicited seeds that show up in their mail. 

“Do not plant seeds from unknown origins,” the CFIA advises in a statement. “Unauthorized seeds could be the seeds of invasive plants, or carry plant pests, which can be harmful when introduced into Canada. These species can invade agricultural and natural areas, causing serious damage to our plant resources.”

No specifics were provided regarding what types of seeds the packages contain, though it’s highly unlikely they are cannabis seeds.

The CFIA is encouraging Canadians to contact their regional agency offices immediately if they receive one of the shipments and to hang on to both the seeds and packaging. 

The Ontario Provincial Police is also warning Canadians not to plant or dispose of the seeds if they receive them, suggesting in a tweet the seeds could be coming in from China or Taiwan. 

Similar packages have also been showing up in the U.S. recently.

The United States Department of Agriculture (USDA) published a statement Tuesday, noting the organization “is aware that people across the country have received suspicious, unsolicited packages of seed that appear to be coming from China.”

The USDA reported that the seeds could be part of a “brushing scam,” where sellers ship cheap, unsolicited products to addresses they find online and then write fake positive reviews in an effort to boost sales. 

The USDA is investigating, alongside the USDA’s Animal and Plant Health Inspection Service, the Department of Homeland Security’s Customs and Border Protection, and other federal agencies.