From southern Ohio down to Alabama and increasingly up the Eastern Seaboard, drug users are dying by the scores in a strange new way: by overdosing on elephant tranquilizer.

The drug, called carfentanil, comes from labs in China—usually mailed to users who buy it online or shipped to cartels in Mexico who smuggle it across the southern border—and is 10,000 times more potent than morphine. Federal law enforcement officials across the eastern half of the country told The Daily Beast they have seen an alarming increase in the number of people dying by overdosing on this drug, and that they’re searching for the toughest prosecutorial strategies to try to stop the deaths.

The problem is metastasizing as Congress pushes for a health care overhaul many experts fear could make the opiate problem even worse. It’s an epidemic that killed more people than car accidents did in 2015, and has federal prosecutors increasingly looking to get offenders responsible for those deaths sentenced to decades in prison—a strategy some prosecutors hope could prevent deaths, but which isn’t without controversy.

The carfentanil deaths started last summer in Northeast Ohio. Though the opioid epidemic has torn through the United States for years, with heroin and prescription painkiller-linked deaths steadily climbing, it took dystopian twist in Akron in July. That’s where people first started overdosing on carfentanil, according to Russ Baer, a DEA special agent who follows the issue. Zoos use the drug to tranquilize elephants and rhinos, and Chinese labs manufacture it and ship it to the U.S. and Mexico, he said. Some American users have it delivered directly in the mail, but law enforcement officials concurred that the bulk of it moves from Chinese manufacturers to Mexican cartel distributors, who ship it up into the United States, often cutting into shipments of heroin, cocaine, or fentanyl (another synthetic opioid that is 50 times stronger than heroin) as a cheap way to make those drugs much stronger. Low-level distributors then sell those drugs to users, who are often unaware that a product they think is just cocaine or heroin includes a secret ingredient that makes it much more potent—and lethal.

Mike Tobin, a spokesperson for the U.S. attorney’s office in the Northern District of Ohio, said users don’t seem to know what’s in the drugs they consume.

“What we’re seeing, anecdotally at least, is it’s amateur hour on the user side and it’s amateur hour on the dealer side,” he said. “We can’t prove it, but the sense is they’re selling whatever they get in the mail from China or that’s coming over the Southern border.”

Baer agreed.

“I can’t imagine that people would deliberately and willfully ingest carfentanil,” Baer said. “It is so outrageously dangerous.”

That hasn’t kept people from ingesting it, and dying by the dozens. It’s proven especially deadly in Ohio and Kentucky, states hit hard by the opioid epidemic. Benjamin Glassman, the U.S. attorney for Ohio’s Southern District, said his office has been charging low-level dealers with federal crimes that carry 20-year mandatory minimum sentences in hopes of deterring the sale of fentanyl and carfentanil. Those sentences only apply when dealers sell to users who then overdose.

Last September, Glassman’s office announced the indictment of two people for selling drugs containing carfentanil to users who then overdosed (though non-fatally). Since then, he said he has seen anecdotal evidence that some dealers in the district are more circumspect about synthetic opioids like fentanyl and carfentanil.

“The deterrent doesn’t last a long time,” he said. “But it will cause a reaction of what we’re seeing on the streets for a period of time.”

And Carlton Shier, the acting U.S. attorney for the Eastern District of Kentucky, said his office has had the same experience—concluding that the threat of lengthy sentences for dealers whose customers overdosed could make them hesitant to sell those drugs.

“When we listen to jail calls, they’re talking about it,” he said. “They’re worried that they’re going to get hammered.”

He said his office has pursued upward of three dozen cases over the last two years charging dealers with lengthy sentences after their customers overdosed. He added that that’s a significant increase from years past, and that carfentanil prosecutions have contributed to the uptick. Trace amounts of the substance can be lethal, he added, and his office has found dealers with significant quantities of it.

“A single gram of this stuff could kill thousands, and we’re getting people with tens of grams,” he said. “It’s pretty awful stuff.”

And that’s informed his office’s view on how to go after dealers.

It’s a controversial strategy. Kevin Ring, the president of Families Against Mandatory Minimums, said there’s scant evidence of a correlation between lengthy prison sentences and lowered drug crime rates, but those sentences are pricey for taxpayers and can separate people from their families for unjustly long periods of time.

“We’ve had federal drug mandatory minimums on the books for 30 years,” he said. “Drug use has remained the same; drug prices have fallen, not risen. Now we’re seeing an explosion in abuse of particular drugs and we’re told we need more of the same of the thing that didn’t prevent the problem in the first place.”

Some U.S. attorneys feel urgency because the problems in their states are getting worse—and fast. Deirdre Daly, the U.S. attorney for Connecticut, said the death toll there was eye-popping: just a handful of fentanyl deaths in 2012, then 188 in 2015, and then more than 446 in 2016. She said carfentanil hasn’t hit her state yet, and that her office hasn’t pushed for the 20-year mandatory minimum charges, but sometimes asks family members of deceased users to give statements to judges before sentencings.

And in the last 12 months, her office has worked on two huge fentanyl cases. Last May, she said her office worked with the DEA and New Britain police to identify a large distributor of fentanyl. They got a Title 3 wiretap and seized 2.5 kilos of the drug and $800,000. Daly said the dealers likely bought the drug from a Chinese lab through the so-called Dark Net. It was the first major fentanyl bust in the state. Then a few days before Christmas, law enforcement officers pulled over a tractor trailer that was headed for Waterbury, Connecticut. It was carrying 55 pounds of fentanyl—a street value of $1.5 million. It was the largest seizure yet in the state, and one of the largest in the country.

But her office doesn’t just focus on massive cases like that. Though federal prosecutors don’t typically go after low-level dealers, she said she instructed police officers to start treating the sites of overdose deaths like crime scenes, gathering evidence to try to find the dealers who sell users the drugs that kill them.

“We decided because people are dying, we had to do something,” she said.

More than 900 people total died by overdosing on drugs in Connecticut last year, she added—more than three times the number of people who died in car accidents in the state. The bulk of those deaths were opioid-related, and fentanyl was a huge part of that.

The federal prosecutors we spoke with concurred that it’s not a problem they can arrest their way out of—an attitude that John Horn, the U.S. attorney in the Northern District of Georgia, said is fairly new. Instead, there’s a consensus that pushing back against the opioid epidemic involves working with community leaders, faith groups, and public health officials, as well as law enforcement. In Atlanta, he said his office and other law enorcement officials have had heartening success working with community leaders to help clean up the English Avenue neighborhood—once a harbor for drug deals. The national implication: Law enforcement can’t fix this alone.

“The problem and its relationship to the abuse of prescription drugs and the addictive nature of the opioids tells me that it’s going to need many more players at the table to solve comprehensively,” he said.

The law enforcement officers we spoke with declined to discuss how the public policy debate roiling Capitol Hill could impact their efforts. Many outside experts concur that the Republican Party’s proposed replacement for the Affordable Care Act could make efforts to counter opioid addiction harder, since it would cut funding for many treatment programs—particularly in Ohio. The New England Journal of Medicine, for instance, published an article earlier this month detailing how people trying to recover from drug addictions in rural communities could have a harder time affording treatment. And on Tuesday evening, news broke that the White House was considering a deal to reduce some requirements on insurance plans as part of that health care overhaul—including requirements that those plans cover addiction treatment.

It’s a problem that’s become as lethal as the HIV/AIDS epidemic, and everyone agrees it demands a comprehensive, multi-pronged approach. The only question is how many people will die by accidentally taking elephant tranquilizer before that happens.