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The chief of a Northern California police department investigating what is suspected to be a mass drug overdose on the fentanyl said they had been “waiting” for this to happen amid reports that the powerful narcotic was heading west.

One person died and another 12 people were hospitalized after the mass overdose at a residence that was reported Saturday morning, Chico Police Chief Michael O'Brien said at a news conference Saturday.

On Sunday, Enloe Medical Center said that of its nine remaining patients from the incident, two were in serious condition, three were in fair condition and four were in good condition, according to reporting from local station Action News Now.

Police suspect the substance involved in the overdoses is fentanyl, a synthetic opioid.

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“We were waiting, and have been waiting unfortunately, for this to happen in the sense that we knew fentanyl had been moving west,” O’Brien said.

O’Brien said that officers had not responded to many fentanyl-related incidents in the past.

“That is changing unfortunately, and now we’ve had this mass casualty incident, like the fire chief said and likely to have been caused from fentanyl,” O'Brien said. “That should concern us all.”

The police chief said that authorities began carrying naloxone, a treatment for opioid overdoses, since 2018 as part of a grant with the local health department and that lives were likely saved in the mass overdose because of it.

O’Brien said officers had responded to many drug overdoses in the past and said naloxone had previously been used in cases of heroin.

Responding officers gave six doses of Naloxone to patients at the site of the incident while also administering CPR, he said. O’Brien added that the outcome would “have been far worse” if the officers did not have or had they not dispensed the antidote.

Two police officers who responded to the scene said they were feeling ill and were transported to the hospital out of an abundance of caution and later released, O'Brien said.

Fentanyl is 50 to 100 times more potent than morphine, according to the Centers for Disease Control. The drug has been blamed for a wave of overdose deaths across the nation.