Colorado Attorney General Cythina Coffman has joined her colleagues in 51 other states and territories in urging Congress to “close a loophole that allows those who traffic deadly fentanyl to stay a step ahead of law enforcement,” according to a Friday press release from her office.

The bipartisan group of attorneys general penned an Aug. 23 letter to Congress in support of the Stopping Overdoses of Fentanyl Analogues Act, which would enable the Drug Enforcement Administration (DEA) to “to proactively add newly modified fentanyl analogues to the controlled substances list,” according to the release.

Fentanyl, which can be used a painkiller, is currently a Schedule II controlled substance. According to the letter, it’s often prescribed to late-stage cancer patients.

“Sadly, fentanyl and its analogues have made their way onto our streets with alarming regularity, and overdosedeaths related to fentanyl now surpass deaths related to heroin,” the letter states.

“The opioid epidemic has devastated communities across Colorado,” Coffman said in the release. “The increasing array of fentanyl analogues starting to creep into our state highlights the need for law enforcement and our partners at the DEA to act quickly to stop the spread of these dangerous drugs to our citizens.”

The letter can be viewed here.