MEXICO CITY — The Obama administration said yesterday that it’s working with Mexico to bring new charges against a drug lord who persuaded a court to overturn his 40-year sentence in the kidnap, torture and murder of a US anti-drug agent.

National Security Council spokeswoman Caitlin Hayden said the United States is deeply concerned by Caro Quintero’s release and is working with Mexican authorities to see that those responsible for the 1985 murder of Drug Enforcement Administration agent Enrique “Kiki” Camarena face justice in the United States.

Quintero left prison Friday and has not been heard from since.