China has hit back at U.S. government's claims that most of the imports of fentanyl, the drug driving America's opioid crisis, are coming from China. China says it will not take the blame for the U.S. own fentanyl abuse problems. The Office of China National Narcotics Control Commission claims the U.S. accusation is baseless and irresponsible. The office says China has taken tougher measures to control fentanyl related substances. From May 1 till now, not a single case of fentanyl trafficking from China to the United States has been identified.