PHILADELPHIA--When it comes to drug overdose deaths in Pennsylvania, heroin no longer tops the list.

Fentanyl now ranks as the top killer drug in the Commonwealth, according to a new report released Thursday by the Drug Enforcement Administration and University of Pittsburgh.

Fentanyl was originally intended as prescription pain medication for cancer patients but now is increasingly being made illicitly and sold on the streets. It was the leading drug found in 52 percent of overdose victims who died in Pennsylvania in 2016.

The 2,395 deaths linked to fentanyl or related substances represented a 130-percent increase from 2015. Some strains are estimated to be up to 6000 times stronger than morphine.

Heroin, meanwhile, was identified in 45 percent, or 2,089 drug overdose deaths last year.

Overall, 4,642 people died in Pennsylvania from drug overdoses in 2016, which amounts to 13 deaths every day_ that's the equivalent of losing an entire soccer team every day.

And what's worse: there are troubling trends tucked within last year's data.

Fentanyl was identified in 32 percent of deaths in January last year, but by December, that figure had steadily climbed to 73 percent, according to the report. (Most victims who died last year, or 84 percent, had the presence of two or more drugs in their systems.)

The biggest increase of fentanyl was found in victims ages 15 to 24, who saw a 380-percent increase compared to other age groups.

Fentanyl is a very dangerous substitute for heroin, according to the Drug Enforcement Administration because it is much more potent than heroin and results in frequent overdoses that can lead to respiratory depression and death.

When fentanyl first emerged on the streets in Pennsylvania in earnest a few years ago, it was cut in with doses of heroin unbeknownst to most drug users. It was cheaper than heroin and boosted a drug dealer's profit margin.

But now, in a relatively new wrinkle, investigators believe "street level traffickers are openly marketing fentanyl to customers instead of disguising it."

It can be hard to know what exactly is being sold as drug dealers seek to increase their customer base by offering higher potency drugs. In Allegheny County, Medical Examiner Karl Williams, said he had seen 1,000 types of uniquely labeled baggies.

"We have no handle on who's mixing this up or who's selling it," he said.

Fentanyl in Pennsylvania mostly comes from clandestine labs in China and Mexico, according to DEA Special Agent in Charge Gary Tuggle. People also can order it over the internet if they know the right dark places to go, he said.

Ninety-five percent of counties that provided data for the annual report had deaths with the presence of fentanyl, including rural counties, illustrating the "widespread availability," and "ease of obtaining...from online sources," according to the report.

Fighting the increase in illicit fentanyl has been getting harder too, because the makers can alter the formulations, as countries seek to ban source chemicals.

In fact, nine out of 10 fentanyl-related substances found in toxicology reports last year were not seen in 2015 reports.

"The rapid introduction of new substances is challenging for toxicologists," according to the report. "The phenomenon is likely the cause of the increased variety...available in Pennsylvania in 2016."

The increase of the potent and volatile fentanyl in toxicology reports is "very bad sign," Tuggle said, indicating that overdose statistics could sink even worse before they get better.

As it stands, the state's drug overdose statistics are exploding. The state reported 2,497 overdose deaths in 2014, 3,376 in 2015 and 4,642 last year.

Officials said they know they can't "arrest" their way out of the problem, and they may not be able to "treat" their way out of the problem either. In the end, they said a change in culture will be required.

Using drugs is not an aversion as it should be, said Janice Pringle, a researcher from the University of Pittsburgh School of Pharmacy who runs the Program Evaluation and Research Unit.

"We can't be so blase about it," she said.

The entire Analysis of Overdose Deaths in Pennsylvania can be found at OverdoseFreePa.pitt.edu.