Originally Published: 02 FEB 23 18:42 ET

Updated: 02 FEB 23 21:07 ET

By Amanda Sealy and Nadia Kounang, CNN

(CNN) -- Sitting among the warehouses of Dulles, Virginia, is one of the US Drug Enforcement Administration's forensic labs. It's one of eight across the country where scientists analyze illegal drugs and try to stay ahead of what's driving deadly overdoses.

Starting in the late 1990s with overprescribing of prescription narcotics, the opioid epidemic has continued to plague the United States for decades. What has changed is the type of drugs that have killed more than half a million people during the past 20 years.

CNN was granted rare access to the secret lab where the DEA tests seized illicit drugs to understand what's coming next.

"The market is constantly changing, so we are trying to do everything we can from a science base to keep up with that," Scott Oulton, deputy assistant administrator of the DEA's Office of Forensic Sciences, told CNN Chief Medical Correspondent Dr. Sanjay Gupta.

Holding a white bag of fentanyl precursor powder -- one of the chemicals used to make the opioid -- Oulton explained that the illicitly made painkiller continues to be a dominant presence in the drugs officials are finding.

"This kilogram can be converted into fentanyl to make approximately 800 grams," he said. "So it doesn't take that much material, it's fairly cheap, it's inexpensive to obtain."

Fentanyl is the deadliest drug in the United States, and it's often found in combination with other illicit drugs, including cocaine and heroin. But increasingly, fentanyl is showing up in illicit pills disguised as common prescription drugs like oxycodone, hydrocodone, even Adderall.

Users buying drugs on the street that look like prescription pills may end up with a highly potent, potentially deadly drug they never intended to take.

"Over 99% of what we see are fake. They contain fentanyl," Oulton says of the pills that the agency is seizing.

The 800 grams of fentanyl that Oulton held could be turned into 400,000 to 500,000 potentially lethal pills.

'He was murdered'

As more and more of these lethal pills circulate, the opioid epidemic is reaching more of the population.

Deena Loudon of Olney, Maryland, is among those living with its effects.

"I truly love sharing Matthew with the world," Loudon says as she flips through pictures of her son.

One of her favorite memories is Matthew playing hockey -- what Loudon calls his happy place.

But she also recalls his struggles with anxiety, which led him to turn to drugs. He started dabbling in them in the 10th grade. By the following year, his grades began to fall, and he couldn't keep them high enough to stay in hockey.

"He was using Xanax to help self-medicate himself and I think to help get rid of some of that angst so he could live somewhat of a normal life," Loudon said.

Matthew was always honest, almost to a fault, Loudon says. "He told me he tried everything. Like everything. Heroin, meth, crack, you name it, cocaine, whatever -- until I guess he found what made him feel the best, and it was Xanax."

And as much as a mother can worry, Loudon says, Matthew always tried to reassure her. "I know what I'm doing," he would tell her.

She had heard about fentanyl showing up in pills in their area.

"But you don't ever think it's going to happen to you," Loudon said.

She said they even had a conversation about fentanyl the day before he died. "I was sort of naive, wanting to stick my head in the sand and thinking 'I bet he does know what he's doing.' "

On November 3, 2020, she found 21-year-old Matthew on the floor of their basement.

Matthew's autopsy report lists his cause of death as fentanyl and despropionyl fentanyl intoxication.

"I don't say he overdosed. I say he died from fentanyl poisoning. ... Truthfully, like, at the end of the day, to me, he was murdered, right? Because he asked for one thing. They gave him something different. And it took his life."

For a parent, she said, the hardest thing is burying their child. It's a pain she speaks out about in hopes of keeping other families safe.

"It's Russian roulette," she warns them. "You never know what you're gonna get."

One pill can kill

The number of pills the DEA has seized skyrocketed in just three years, from 2.2 million in 2019 to 50.6 million in 2022.

The sheer volume of pills has been one of the biggest challenges for the DEA's lab, Oulton says. As the fentanyl threat continues to grow, the Virginia facility is expanding to accommodate the analysis needed.

The lab can test for something as simple as the presence of fentanyl, but something called the purity of the pill also offers important insight. This means how much fentanyl is actually in one of these illicit pills.

"Lately, we've been seeing a purity increase over the last year, where we used to say roughly four out of the 10 seizures that we were receiving would contain a lethal dose of greater than 2 milligrams. As of October last year, we started reporting that we've seen an uptick. Now we're saying that six out of 10 of the seizures that we're receiving contain over 2 milligrams," Oulton said.

He says they're finding an average of 2.3 milligrams of fentanyl in each pill.

Two milligrams may be the cutoff for what is considered lethal, but Oulton says that doesn't necessarily mean a pill with 1.99 milligrams of fentanyl can't be deadly.

"One pill can kill" is his warning.

"The message I would like to send out is, don't take it," he said. "Don't take the chance. It's not worth your life."

More pills, new drugs

Oulton says he and his team are constantly finding new and different drugs and substances in pills -- things they've never seen before.

One machine in the lab is almost the equivalent of an MRI in a medical office, showing the structure and detail of a pill.

"We will do what we call structural elucidation to determine that this is a different version of a fentanyl that's got a new compound and molecule that's been added to it," Oulton said.

They've seen "hundreds and hundreds of unique combinations," he said.

"We'll see one that contains fentanyl, one with fentanyl and xylazine, one with fentanyl and caffeine, one with fentanyl and acetaminophen, and you don't know what you're getting."

Xylazine, a veterinary tranquilizer, poses a unique problem. It's not an opioid, so even when it's mixed with fentanyl, drugs designed to reverse an opioid overdose may not work.

Narcan or naloxone, one of the more common overdose-reversing drugs, has become increasingly necessary as the prevalence and potency of illicit drugs increases. About 1.2 million doses of naloxone were dispensed by retail pharmacies in 2021, according to data published by the American Medical Association -- nearly nine times more than were dispensed five years earlier.

Oulton wants to be clear: The problem Isn't with pills prescribed by your doctor and dispensed by a pharmacy -- it's the pills on the illicit market.

Those, Matthew's mother warns, are easy to get.

"The first pills [Matthew] got was in high school. And it was just flipping out, floating around, and it was easy for him to get his hands on," she said.

Loudon's message for parents now: Keep your eyes open.

"Just be mindful of what your children are doing. You just just have to keep your eyes open. And even sometimes, when you keep your eyes open, you can miss some of the warning signs, but I think a parent knows their child best, so just keep talking."