The Drug Enforcement Administration issued a warning Monday about “dangerous” counterfeit pills from Mexico that are “killing Americans.”

The federal law enforcement agency said that Mexican drug cartels are manufacturing mass quantities of the bogus prescription pills containing fentanyl – a highly addictive synthetic opioid that is lethal in minute doses – for distribution through North America.

Based on a sampling of tablets seized nationwide from January to March of this year, the DEA found that 27 percent contained potentially lethal doses of fentanyl.

“Capitalizing on the opioid epidemic and prescription drug abuse in the United States, drug trafficking organizations are now sending counterfeit pills made with fentanyl in bulk to the United States for distribution,” said DEA Acting Administrator Uttam Dhillon in a statement.

“Counterfeit pills that contain fentanyl and fentanyl-laced heroin are responsible for thousands of opioid-related deaths in the United States each year.”

The DEA noted that fentanyl and other highly potent synthetic opioids are the main force behind the country’s ongoing opioid crisis with fentanyl involved in more deaths than any other illicit drug.

DEA Special Agent in Charge Ray Donovan of the New York Division added: “Fentanyl analogues are the most dangerous drugs on the street because they are man-made, cheap, and unlimited.”

“Counterfeit pills have hidden dangers causing one in four users to die, according to DEA field testing,” Donovan said. “This is a warning to New Yorkers and a plea for parents to talk to their children about using counterfeit or diverted prescription pills- either one of them ends with death and/or devastation.”

According to the DEA, a lethal dose of fentanyl is estimated to be about two milligrams.