Authorities have seized over 20 million fake opioid pills containing fentanyl so far this year, the Wall Street Journal reported Thursday.

These pills are largely disguised as medications but really contain fentanyl manufactured by Mexican cartels, according the Wall Street Journal. Many of these pills are also mass-produced by Mexican drug cartels using the manufactured fentanyl.

“The supply of these pills is going up exponentially,” Joseph Palamar, an associate professor and drug epidemiologist at New York University Langone Health, told the WSJ. “They are easy to transport and difficult to track. Pills are the ultimate fake out. You can fake out your parents, your friends, your partner, law enforcement.”