Both officers were treated and released.
At a news conference, Chico, California police captain Mike O'Brien said one man died at the scene and four other victims are in critical condition, reported NBC News. "That is yet to be confirmed, but we do anticipate confirmation in the coming days".
The drug is so potent that two officers who responded to the home started to feel its effects and were transported to a hospital for examination, then released.
The victims - aged 19 to 30 - all became ill yesterday after taking the powerful drug fentanyl.
Chico Police Department did not immediately respond to Newsweek's request for comment.
As of about 10 pm last night, nine people were still in the hospital, four in critical condition, two in serious condition, and three in fair condition.
"Remember, the amount of carfentanil - these substances are extremely unsafe - and it takes just a very minute amount to cause life-saving conditions", O'Brien said.
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Meanwhile, it's not clear where the Fentanyl originated and if there are more batches being sold around Chico, O'Brien said. It blocks or reverses the effects of opioids and is often carried by first responders. O'Brien said a narcotics task force was trying to determine the source of the drugs.
O'Brien said that numerous overdoses in Chico involve heroin, but not Fentanyl, adding that it's worrying to see the powerful drug in the city.
"That is changing, unfortunately", He said, "and now we've had this mass casualty incident ... likely to have been caused by fentanyl". "That should concern us all".
Fentanyl is a synthetic opioid that is 80-to-100 times stronger than morphine, according to the US Drug Enforcement Administration.
The shipment of fentanyl from China to the U.S.is "almost a form of warfare", Trump said in August. A report issued by the Centers for Disease Control in December showed fentanyl was the leading cause of overdose deaths in the USA for 2016, the most recent year numbers have been released.
The majority-or least 68 percent-of those deaths could be attributed to opioids such as fentanyl.