DEA agents in San Antonio say fentanyl is flooding into the city. The synthetic opioid is mostly manufactured in China and Mexico these days and then mixed in with other illicit drugs. Most of the fentanyl in San Antonio is in the form of fake prescription pills, such as phony hydrocodone or oxycodone. These pills are made by clandestine drug manufacturers, not under laboratory conditions. Many pills end up at parties on college campuses, where students can die from a one-time use, since even small amounts of fentanyl are deadly.