(Yicai Global) Dec. 3 -- Two pharmaceutical firms listed in China have denied exporting fentanyl, an addictive opioid used in painkillers, to the United States after China said it would examine its control of the drug.

Humanwell Healthcare Group has not exported the drug, or its intermediates or ingredients, to the US, the Hubei-based firm said in a statement yesterday. Jiangsu Nwha Pharmaceutical also told the Securities Times that it would "not be affected" because it only uses fentanyl for production, and does not sell it.

China and the US have agreed to cooperate in law enforcement and drug control over fentanyl products, China's State Councilor and Foreign Minister Wang Yi said at a press briefing in Buenos Aires on Dec. 1, during the G20 summit meeting.

"It is outrageous that Poisonous Synthetic Heroin Fentanyl comes pouring into the U.S. Postal System from China," US President Donald Trump said in August. "We can, and must, END THIS NOW! The Senate should pass the STOP ACT – and firmly STOP this poison from killing our children and destroying our country. No more delay!"

Some 68,255 people died from drug overdoses in the 12 months leading April 2018, according to data from the US Centers for Disease Control and Prevention. Around 29,116 of those were related to synthetic opioids like fentanyl.

Humanwell subsidiary Yichang Humanwell specializes in fentanyl products and generated over CNY2 billion (USD287 million) from their sales last year, with about CNY5 million (USD718,412) worth going to Sri Lanka, Ecuador, the Philippines, Turkey and other countries and regions, it said. Its buyers are national official procurers, officially recognized local firms with appropriate licenses or local factories qualified to use the drug, the firm added, saying it strictly monitors purchasers' legal rights to obtain such products.