MONTERREY, Mexico (Reuters) - The U.S. Treasury Department said on Wednesday it had frozen assets belonging to an alleged accomplice of Rafael Caro Quintero, a Mexican drug trafficker who tops the U.S. Drug Enforcement Administration’s most wanted list. Caro Quintero, who has a U.S. $20 million award on his head, spent years in a Mexican prison for the killing of U.S. Drug Enforcement Administration (DEA) agent Enrique “Kiki” Camarena in 1985, but was freed several years ago.