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Illegal, lab-made fentanyl helped kill at least half the people who died of opioid overdoses in 2016, the Centers for Disease Control and Prevention reported Friday.

The report demonstrates just how deadly the opioid epidemic has become. These synthetic fentanyl-like drugs are extremely potent.

It also shows that the most lethal effects of the opioid epidemic are coming from the streets and not out of doctors’ offices and pharmacies, the CDC team said.

“Illicitly manufactured fentanyl is now a major driver of opioid overdose deaths in multiple states, with a variety of fentanyl analogs increasingly involved, if not solely implicated, in these deaths,” the CDC’s Julie O’Donnell, John Halpin, and colleagues reported.

“Fentanyl was involved in more than 50 percent of opioid overdose deaths, and more than 50 percent of deaths testing positive for fentanyl and fentanyl analogs also tested positive for other illicit drugs.”

It’s the first report using evidence from the toxicology and on-the-scene reports of opioid overdose deaths.

President Donald Trump declared the opioid abuse epidemic a public health emergency on Thursday, a short-term order that provides little money to help fight the crisis.

Related: Trump Calls Opioids ‘Worst Drug Crisis in American History’

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Synthetic opioid overdoses killed 20,000 people in 2016, the CDC says.

The CDC team said one important step is finding out which drugs are killing people. So they dug up blood tests done on people who died of overdoses in 10 states.

They found a troubling number of deaths from highly potent drugs related to fentanyl, called fentanyl analogs.

“The fentanyl analogs most commonly detected were carfent­anil, furanylfentanyl, and acetylfentanyl,” they wrote.

Fentanyl is a drug that was originally designed to be used to ease the most extreme pain — among people dying of cancer, for instance. The analogs are even more potent.

“Illicitly manufactured fentanyl is now a major driver of opioid overdose deaths in multiple states."

“With few exceptions, fentanyl analogs are illicitly manufac­tured, because they do not have a legitimate medical use in humans,” the researchers wrote.

These drugs were found so frequently, the researchers said, that it makes them fear they’re being used commonly across the country. “This finding raises concern that in the near future, fentanyl analog overdose deaths might mirror the rap­idly rising trajectory of fentanyl overdose deaths that began in 2013 and become a major factor in opioid overdose deaths,” they wrote.

Related: Fentanyl: Stronger Than Heroin

Ohio Attorney General Mike DeWine, whose state has been especially hard hit by opioid abuse, told a joint committee of Congress last June that drug dealers add the synthetic opioids to heroin or other, more common street drugs to have something new and fresh to offer buyers. “It’s all about customer service,” DeWine said.

That means buyers don’t always know what they are getting, something that makes overdose far more likely.

“Because of its extreme potency, even limited circulation of carfentanil could markedly increase the number of fatal overdoses,” the CDC team said.

Related: Fentanyl Easily Available Online

“Previous reports have indicated that use of illicitly manufactured fentanyl mixed with heroin, with and without users’ knowledge, is driving many fentanyl overdoses, particu­larly east of the Mississippi River,” they added.

“Consistent with these findings, at least half of opioid overdose deaths in six of the seven participating states east of the Mississippi tested positive for fentanyl.”

And people are mixing drugs. “The increased mixing or co-use of fentanyl, heroin, cocaine, and varying fentanyl analogs might contribute to increased risk for overdose because persons misusing opioids and other drugs are exposed to drug products with substantially varied potency,” the team said.