Counterfeit drugs sold online are increasingly being laced with fatal doses of fentanyl, The Wall Street Journal reports. Counterfeit Xanax is a particular concern, experts told the newspaper.

Officials have found counterfeit drugs made with fentanyl in 44 states, according to Shabbir Safdar, Executive Director of Partnerships for Safe Medicines, a San Francisco-based nonprofit. Officials have confirmed fentanyl in counterfeit drugs to be a cause of death in 26 states. “Right now you’re seeing Xanax and opioids like oxycodone and hydrocodone made both overseas and domestically with fentanyl, which is super cheap and easy to get,” he said.

The National Association of Boards of Pharmacy (NABP) reviewed 12,000 online drug outlets selling prescription medications to U.S. patients. Of these, about 95 percent were found noncompliant with state and federal laws and NABP standards, according to a report published last month.