VIENNA (AP) — The U.N.’s Commission on Narcotic Drugs has imposed controls on the production, sale and export of some substances used for the illicit manufacture of fentanyl, a deadly opioid that kills thousands of people a year in the United States.

A prescription painkiller, fentanyl is up to 50 times stronger than heroin. It is often mixed with heroin or made to look like other painkillers that fetch a higher street price, with fatal results for users unaware that it has been added.

The U.S. Centers for Disease Control attributes more than 33,000 deaths in the United States to overdoses involving opioids obtained either illicitly or through prescriptions in 2015. A fentanyl overdose killed pop star Prince last year.

A U.S. statement said Thursday’s decision would have a “clear benefit for the United States.”

Copyright 2017 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.