WASHINGTON - The U.S. Drug Enforcement Administration issued its first public alert in six years warning about a surge in fake prescription pills on the market containing fentanyl and methamphetamine, which is killing Americans at an "unprecedented rate."The agency on Monday reported the "significant nationwide surge in counterfeit pills," saying the fake medication is being mass-produced by criminal drug networks in labs and made to look like legitimate prescription pills such as Percocet, Xanax and Adderall.The DEA said the fake pills are "killing unsuspecting Americans at an unprecedented rate," noting that two out of every five fake pills with fentanyl contains a potentially lethal dose, an assessment based on DEA lab analyses of seized.