A new study from the Centers for Disease Control and Prevention released Friday found the street drug xylazine surged much earlier than previously reported.

The CDC concluded that by 2021, the "rate of drug overdose deaths involving xylazine was 35 times higher than the 2018 rate."

But the report shows the explosion of xylazine-related deaths began in 2018 with overdose fatalities rising to 627 in 2019 — doubling to 1,499 in 2020 — and then doubling once more to 3,468 in 2021.

This spring, the Biden administration declared illicit xylazine, also known as tranq on the street, an "emergent" threat.

At the time, officials warned the chemical, used by veterinarians as a horse tranquilizer, was spreading fast in street drugs, causing overdose deaths and terrible flesh wounds in people struggling with addiction nationwide.

"I'm deeply concerned about what this threat means for the nation," said Dr. Rahul Gupta, head of the White House Office of National Drug Control Policy when speaking to reporters in April.

Public health officials say it remains unclear why so many drug dealers began using xylazine as an additive.

Men suffered xylazine-related deaths at twice the rate of women, and Black men appeared particularly vulnerable.

Because drug death data is gathered and analyzed slowly, it's impossible to say with clarity what has happened in the months since 2021. But government officials say there are troubling indicators.

When data for this report was collected, illicit xylazine use was still largely concentrated in the mid-Atlantic states and the Northeast.

According to the White House Office of National Drug Control Policy, xylazine is now turning up in street samples collected across the U.S., surging in the South and West.

Speaking earlier this month Dr. Nora Volkow, head of the National Institute on Drug Abuse, said public health data on rapidly spreading street drugs like xylazine is often dangerously outdated.

"What is happening right now? I don't know," Volkow told NPR.

"If you want to actually be nimble and flexible and do the interventions on the basis of what you are observing, you need timely data," she said. "Otherwise, you're doing it with your eyes closed."

In most cases, drug policy experts say xylazine is mixed by dealers in a high-risk cocktail with fentanyl, methamphetamines or other illicit drugs.

On Thursday, the CDC released a separate report finding that by 2022, xylazine was being detected in nearly 11% of all fentanyl-related overdoses.

"These data show that fentanyl combined with xylazine is increasingly dangerous and deadly," Gupta said in a statement Thursday.

Xylazine has been widely used for years as a horse tranquilizer. Some in Congress are scrambling to tighten regulations and criminal penalties for misusing the chemical.

U.S. drug deaths, fueled largely by fentanyl but also increasingly by complex street drug cocktails, hit another devastating new record last year, with roughly 110,00o fatal overdoses nationwide.