SAN FRANCISCO (AP) — Federal and San Francisco authorities say they seized more than 12 pounds of the deadly narcotic fentanyl in what they characterized as a major drug bust.

Authorities announced federal conspiracy charges against eight people suspected of supplying drug operations in the city's troubled Tenderloin neighborhood.

The Tenderloin is a diverse district which is home to government buildings, theater venues, families with children living in apartments and homeless people. It's also a neighborhood where dealers sell drugs in the open and users shoot up drugs in public.

San Francisco Police Chief Bill Scott on Tuesday called overdose deaths fueled by cheap and potent fentanyl a public health calamity.