San Francisco health officials issued a warning Thursday following a spike in fentanyl overdoses in which users were exposed to the opioid while using cocaine. 

The city's health department said it was alerted to three incidents in the past two weeks in which people were using cocaine and "were unintentionally exposed to fentanyl."

Another nine similar non-fatal events occurred in two groups of people, the agency said. 

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A bag of fentanyl pills worth $85,000, according to CBP. 

A bag of fentanyl pills worth $85,000, according to CBP.  (Twitter/@USBPChiefTCA)

Fentanyl overdoses have increased in San Francisco since 2015, with an estimated 474 deaths in 2021, the Health Department said. The deaths usually involved the presence of other drugs, the agency said, such as cocaine and methamphetamine. 

"The similar appearance of fentanyl and stimulants may lead to unintentional use of fentanyl among people who use stimulants and have little or no tolerance to opioid," the warning said. 

The three people who died apparently used the drug in the city's Mission district, Supervisor Hillary Ronen tweeted earlier this month. 

"The tragedy of this crisis knows no bounds," she wrote. "We must do everything in our power to save people from this deadly epidemic."

Tenderloin district in San Francisco drug use fentanyl

Roger Boyd, 35, holds a piece of foil containing Fentanyl while spending time on McAllister Street in the Tenderloin district of San Francisco, Calif. The city's health agency issued a warning Thursday after learning of three fentanyl-related overdose deaths within the past two weeks. (Photo by Jessica Christian/San Francisco Chronicle via Getty Images)

Fentanyl, which can be up to 50 times more potent than heroin is often sold in powder form, the Health Department said. Last week, five West Point cadets vacationing in Florida for spring break overdosed on fentanyl-laced cocaine, authorities said. Four were hospitalized. 

In December, San Francisco Mayor London Breed announced a plan to combat crime and drug use, specifically in the troubled Tenderloin neighborhood. In 2020, the city experienced 700 drug overdose deaths, she said.

Her state of emergency for the neighborhood ends this week after authorities spent 90 days allocating resources there but an additional 20 police officers have been assigned to the Tenderloin to address crime and drug dealing. 

Travis Hayes, 65, injects what he says is the synthetic drug fentanyl on Feb. 27, 2020, across the street from where San Francisco mayor London Breed held a news conference introducing legislation to curb the rise of deadly overdoses in the city, at the Tenderloin section.  

Travis Hayes, 65, injects what he says is the synthetic drug fentanyl on Feb. 27, 2020, across the street from where San Francisco mayor London Breed held a news conference introducing legislation to curb the rise of deadly overdoses in the city, at the Tenderloin section.   (Reuters/Shannon Stapleton)

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"Since the emergency was declared, thousands of people have been referred to health and human services, hundreds have received shelter, and tons and tons of trash and debris have been removed from the streets," Breed said in a statement Wednesday. "While we’ve made noticeable progress, we’ve made a commitment to the Tenderloin community and we’re continuing our emergency response."