Updated

Officials say at least a dozen people in the Sacramento, California area have fatally overdosed on a pill disguised as a popular painkiller, and similar pills also have turned up in the San Francisco Bay Area.

A report released Tuesday by the Centers for Disease Control and Prevention says Bay Area hospitals have treated seven patients in recent weeks who ingested what they thought was the painkiller Norco. Those patients survived.

The pills were adulterated with the powerful opioid, fentanyl.

Sacramento County health officials have reported 52 poisonings related to the pills since late March, with 12 resulting in deaths.

Law enforcement officials are investigating the source of the pills.

Drug Enforcement Administration Special Agent Casey Rettig said she was not aware of any similar cases elsewhere.