The U.S. Treasury Department on Tuesday designated 28 people and entities in China and Canada allegedly involved in the large-scale manufacture and distribution of fentanyl in the U.S.

The action freezes assets held by those designated and prohibits Americans from transacting with them. Deputy Secretary Wally Adeyemo said the department would also pursue friends and family members of the designated individuals who stand to gain from the sale of illicit drugs.

“If you benefit from the proceeds of this illicit activity, we are going to come after your assets,” he said at a press conference, according to his prepared remarks.

The Biden administration has come under pressure from critics, including Republican presidential candidates, over the flow of fentanyl and its precursors into the U.S. from China and frequently through Mexico. 

The sanctions are the result of investigations performed by the Treasury’s Office of Foreign Asset Control, the Financial Crimes Enforcement Network and the Internal Revenue Service.