I just looked it up and found this DEA report published in 2018 - https://www.dea.gov/sites/default/files/2018-07/BUL-039-18.p...

> Forensic chemists discovered fentanyl and fentanyl-related substances including acetyl fentanyl, carfentanil, Furanylfentanyl, and p- fluoroisobutyryl fentanyl in over 180 cocaine exhibits.