Did U.S. Agents Offer a Mexican Drug Suspect Immunity?

A Mexican drug suspect awaiting trial in Chicago on smuggling charges is now saying he can't be prosecuted -- because he worked as an informant for the U.S. government and was promised immunity.

The report could be just the latest major embarrassment for the Drug Enforcement Agency as congressional leaders continue to probe the Operation Fast and Furious gunwalking scandal.

According to CBS News' Sharyl Attkisson -- the same reporter who said a White House official "screamed" and "cussed" at her for her "Fast and Furious" coverage -- Vicente Zambada-Niebla said Drug Enforcement Agents gave him and other Sinaloa cartel leaders "carte blanche" to "operate their drug business without interference" as long as they informed on other cartels.

CBS reported:

Prosecutors say Vicente Zambada-Niebla oversaw drug running on a massive scale into the U.S. But now, from behind bars at a maximum security prison in Chicago, he's making his own explosive accusations -- that U.S. government agents have been aiding Mexico's infamous Sinaloa cartel -- even tipping off leaders on how to avoid capture.

Agents are denying they offered immunity, and Phil Jordan, the former head of the DEA's Center for Drug Trafficking Intelligence, told CBS the agency doesn't have the authority to make such a deal anyway.

"We do not have the power to offer immunity," he said.

But according to CBS, court documents show the U.S. did have a signed cooperation agreement with a different Sinaloa leader:

That agreement was with Sinaloa cartel lawyer Humberto Loya-Castro. Starting as early as 2004, Loya passed information to the DEA from cartel leaders including Zambada -- the one now on trial. In return, Zambada claims, the U.S. dismissed a major case against Loya and agreed to "not ... interfere with" the cartel's "drug trafficking" or actively prosecute their leadership.

Jordan told CBS only that such a deal was "probably a matter of trying to get inside or closer intelligence to the whole Mexican federation, as we call it."

Zambada's claims come amid a New York Times report that the U.S. is increasingly infiltrating dangerous Mexican gangs with "significantly" built-up networks of informants.

Prosecutors told CBS that even if agents did offer Zambada immunity it could not be enforced.