WASHINGTON–House lawmakers Wednesday morning will undertake one of their most arduous ambitions in Congress, trying to stop the flow of deadly fentanyl into the U.S. – a drug trafficking supply chain so dangerous it has created the leading cause of death in Americans ages 18 to 45.

More than 70,000 people died of a fentanyl overdose in 2021, according to the most recent federal data available. That's more than double the amount in 2019 and a large share of the nearly 107,000 drug overdose deaths in 2021.

"It is the deadliest drug threat our country has ever faced," Drug Enforcement Agency  Administrator Anne Milgram said in a Senate hearing Feb. 15. "Fentanyl is everywhere. From large metropolitan areas to rural America, no community is safe from this poison."

At 9 a.m. Wednesday, a House Judiciary subcommittee will examine the issue.

Congressional Republicans have tied the fentanyl crisis to a surge of illegal border crossings, but Democrats say that is misinformation that conflates migrants seeking asylum with a dangerous influx of fentanyl trafficking.

Border Patrol and the DEA say the overwhelming majority of fentanyl is trafficked through legal ports of entry by U.S. citizens driving cars and commercial vehicles, hiding the illicit drugs among other goods.

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What is fentanyl?

Fentanyl is a synthetic opioid so powerful that it is up to 50 times stronger than heroin and 100 times stronger than morphine, according to the U.S. Centers for Disease Control and Prevention.

It is highly addictive and deadly, even in the smallest quantities.

Fentanyl is often found in counterfeit pills – deceptively made to look like prescription drugs – and other illegal drugs. It is frequently mixed in with other drugs, such as marijuana, cocaine, methamphetamine and heroin. Even trace amounts can kill the user.

It is nearly impossible to tell if street drugs are laced with fentanyl unless they are tested, according to the CDC.

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Where is fentanyl made?

The supply chain mainly traces to China, where chemicals in fentanyl are mass produced.

Those chemicals are then typically sent to Mexican cartels, which turn them into fentanyl powder and pills that are often made to look like prescription drugs.

Fentanyl typically enters the U.S. from Mexico through ports of entry in low concentration, high-volume loads, according to the DEA. Deadly doses can move in tiny quantities and are sometimes shipped by mail. However, fentanyl is often hidden among legal goods and trafficked by U.S. citizens driving cars and tractor trailers.

In fiscal year 2022, more than 14,000 pounds of fentanyl, or hundreds of millions of doses, was seized at the U.S.-Mexico border, according to Customs and Border Protection.

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Biden administration officials told senators last week how the fentanyl pipeline increases the challenges they face in stopping the surge of deaths. They also said China and Mexico need to cooperate more with the U.S. to reverse the increase in fentanyl deaths.

"We believe Mexico needs to do more to stop the harm that we're seeing," Milgram said.

Todd Robinson, assistant secretary for the Bureau of International Narcotics and Law Enforcement Affairs, said the U.S. has had "very limited engagement with China" about fentanyl. "We have a number of issues to discuss with them."

Fentanyl poisoning 'a national crisis'

The latest trend in the fentanyl crisis is one of the most disturbing to lawmakers and law enforcement: kids are being poisoned.

Many of the opioid deaths among teens happen after they buy drugs illegally through social media, such as prescription pain killers like Percocet, unaware that they contain fentanyl. Some of them have taken a pill for the first time – not knowing it's counterfeit and full of fentanyl – and have died.

In 2022, the DEA seized more than 50 million poisoned pills.

When someone dies after taking one of the counterfeit pills, Milgram calls them drug poisonings, not overdoses, because people are tricked into consuming fentanyl.

From September 2021 through August 2022, more than 107,000 people died of drug poisonings in the United States, Milgram said.

"Every day, 294 people die from drug poisonings," she said. "Countless more people are poisoned and survive. These drug poisonings are a national crisis."

The DEA, now in year two of its "One Pill Can Kill" campaign, is focusing most of its efforts on trying to dismantle the Mexican cartels that are driving U.S. drug poisonings, Milgram said.

Candy Woodall is a Congress reporter for USA TODAY. She can be reached at cwoodall@usatoday.com or on Twitter at @candynotcandace.

This article originally appeared on USA TODAY: Fentanyl hearing investigates overdose deaths, how drugs cross border