U.S. Customs and Border Protection officers are seizing a record number of pill presses used to make counterfeit drugs, CNN reports.

Pill presses allow someone to take powder and press it into a pill. Most of the pill press machines come from China, the article notes. Much of the illegal fentanyl that is coming into the country also comes from China. The presses are being used to mix fentanyl with drugs such as oxycodone or Xanax. These counterfeit pills can be deadly.

“People have died from ingesting what they think is a legitimate painkiller, (but really) it’s a counterfeit pill that contains fentanyl,” said John Martin, special agent in charge of the Drug Enforcement Administration’s San Francisco division. “To the naked eye, you can’t tell the difference. If you have counterfeit pills, you can’t make them without pill presses.”