Where the fentanyl flooding San Francisco streets is coming from kcra.com - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from kcra.com Daily Mail and Mail on Sunday newspapers.
A UCSF expert says that interrupting the supply chain for illegal fentanyl, most of which comes out of Mexico, is far more difficult than just busting dealers and seizing their inventory.