Fentanyl pills. AP/Cuyahoga County Medical Examiner's Office Chinese laboratories are producing and openly selling a new form of deadly fentanyl to get around China’s recent export ban on the synthetic drug causing thousands of overdose deaths across the United States.

The slightly tweaked version of fentanyl — called furanyl fentanyl — is so new that it is not on the US government’s list of controlled substances.

That means the altered fentanyl, which was blamed for the March overdose of an Illinois man, is technically legal for drug dealers to sell.

The US Drug Enforcement Agency told STAT Monday that it is moving quickly to ban street sales of the new fentanyl product.

The agency plans within days to classify furanyl fentanyl as an analog to fentanyl, which would mean the new drug would be treated in the same fashion as fentanyl, said DEA spokesman Russell Baer.

He added that the producers of the new fentanyl are located in China and said the agency is planning similar action with other fentanyl analogs it has identified.

Fentanyl can be legally prescribed by physicians, often to treat chronic pain. Any other sale of the drug is illegal.

The DEA is also working to place the new version of fentanyl on the permanent list of controlled substances, a move that requires review by the Food and Drug Administration, Baer said. The chemical structure of the new drug, and its effect on the body’s central nervous central system, is nearly identical to that of fentanyl. China last fall banned more than 116 synthetic drugs, including other analogs of fentanyl. One of the most popular of those is called acetyl fentanyl.

Once the ban was in place, furanyl fentanyl began to show up in the United States.

“Laboratories are automatically tweaking the formula to come up with the next analog,” said Baer. “We will seek to put furanyl fentanyl on the list (of controlled substances), and then they will tweak one molecule, and in two months we will be discussing that one. It is a challenging process for us.”

A laboratory company called Dharma Chemicals, or Dharmachem, that reports an address in a central China commercial district, recently told a STAT reporter by email that is was no longer selling the banned acetyl fentanyl, but that it “just added” furanyl fentanyl to “our catalogues.” The company said the drug was being sold for “laboratory research.”

The company was previously accused in a World Health Organization report of selling acetyl fentanyl over the Internet.

The company lists its headquarters headquarters in the Chinese city of Wuhan. Thomson Reuters

Furanyl fentanyl was recently identified as the cause of death in the fatal overdose of a 30-year-old man in Naperville, Ill., a suburb west of Chicago, according to an overdose database maintained by the Will County coroner. It appears to be the first public reporting of a case in which the new version of fentanyl caused a deadly overdose.

In many areas of the United States and Canada, fentanyl is now causing more fatal overdoses than heroin. The drug is up to 100 times more potent than morphine and many times stronger than heroin. In some cases, fentanyl is being sold in pill form, often made to look like other prescription painkillers that fetch a higher price on the street. Fentanyl is also being added to heroin. Users are often unaware they are snorting or injecting the more powerful fentanyl.