In 2018 alone, nearly 32,000 American men, women and children fatally overdosed on a synthetic opioid. One of the deadliest synthetic opioids is fentanyl, which is helping to drive our nation’s opioid crisis.

Fentanyl is 50 times more potent than heroin and 100 times more potent than morphine. There are also countless types of fentanyl analogues, which are similar in chemical structure to fentanyl, but can be even more potent. Carfentanil, the most powerful fentanyl analogue detected in the United States, is estimated to be 10,000 times more potent than morphine.

Although commonly used as a tranquilizer for elephants and other large mammals, drug traffickers mix carfentanil or other fentanyl-related substances with heroin or other illicit drugs to make the drugs stronger.

Now, a critical tool that, for two years, has allowed law enforcement to combat trafficking of the fentanyl-related substances is set to expire unless Congress passes permanent legislation within the next few weeks.

Fentanyl and fentanyl-related substances have had a particularly destructive impact in Chicago and cities and suburbs across the nation.

The illegal trafficking of opioids and other drugs continues to fuel Chicago’s stubborn violent crime problem. Murders, shootings, robberies and other violent crimes, such as the illegal use, possession and transfer of firearms, are often a byproduct of the illicit drug market.

To fight this violence-ridden drug trade and stem the tide of opioid overdoses, law enforcement needs access to every available tool.

A crisis of this magnitude demands nothing less.

Unfortunately, we are in danger of losing a critically important legal tool unless Congress acts quickly to keep potent fentanyl analogues illegal under federal law.

Prior to 2018, drug traffickers created new fentanyl-like drugs, often by altering a single molecule in their formulas, in an attempt to skirt U.S. law, which had outlawed only a few fentanyl analogues. These new substances fell outside of U.S. control, requiring the Drug Enforcement Administration to restart the tedious process of identifying and controlling them on a substance-by-substance basis.

Law enforcement and prosecutors were given the difficult task of keeping up with ruthless and well-financed drug traffickers and their unscrupulous chemists.

In response, the DEA instituted — on an emergency basis — a temporary, two-year control of all “fentanyl-related substances.” As a result, anyone who manufactures, imports, distributes or possesses a fentanyl-related substance is subject to federal criminal prosecution. This emergency order has been a tremendous help as we work to combat the epidemic and prosecute and deter distributors responsible for peddling deadly fentanyl analogues.

However, the DEA’s temporary scheduling of fentanyl analogues on a class-wide basis is set to expire Feb. 6. This means that, unless Congress acts within a few weeks, drug traffickers will be incentivized to create and distribute modified versions of fentanyl.

That’s exactly what happened prior to the DEA’s emergency scheduling of fentanyl-related substances in 2018.

We can’t let that happen again.

Congress needs to pass legislation ensuring that permanent, class-wide scheduling of fentanyl analogues continues. This can be done without impeding responsible medical research or interfering with medically necessary prescriptions.

Following the U.S.’s lead, China — one of two principal sources of fentanyl-related substances to our country — imposed a similar class-wide control on all fentanyl-related substances last year. That action marked a significant development in the worldwide fight against opioid trafficking.

It is now up to Congress to take the next step in this fight. It needs to act soon. Lives are at stake.

John R. Lausch Jr. is the U.S. attorney for the Northern District of Illinois.