In a shocking development in the Operation Fast and Furious investigation, documents show Bureau of Alcohol, Tobacco, Firearms and Explosives agents allowed grenade parts to walk in addition to guns.

The emails also show Obama administration officials acknowledging that they may lose track of grenades but would still be able to accomplish their original objective even if the grenades explode.

According to an internal email that was provided to Congress by the Department of Justice and first reported by CBS News’ Sharyl Attkisson — who’s been the media’s most dogged reporter in tracking down facts on Fast and Furious — ATF began watching accused smuggler Jean Baptiste Kingery’s AK-47 purchases in 2004. In the 2009 internal ATF email, Obama administration officials admitted they believed Kingery was “trafficking them into Mexico.”

The 2009 email shows the ATF officials had then become aware of Kingery’s alleged grenade trafficking.

The administration officials then put together a plan: They secretly intercepted Kingery’s grenade parts after he ordered them online, marked them with special paint and gave them back to him. Then, they allowed him to take those grenade parts into Mexico. ATF was going to try to find his weapons factory there — even though the U.S. government and its federal law enforcement agencies have no jurisdiction in Mexico — with the apparent goal of building a bigger case against Kingery.

ATF agents had planned to work with Immigration and Customs Enforcement officials — who, unlike ATF agents who ultimately report to Attorney General Eric Holder, report up the chain to Homeland Security Secretary Janet Napolitano. (RELATED: Full coverage of Operation Fast and Furious)

The emails show ATF agents were aware they might lose track of Kingery while they allowed him to transport the grenade parts into Mexico. The emails also show ATF agents knew that the grenades could end up exploding and killing innocent people if they proceeded with the plan. That didn’t stop the Obama administration’s ATF from allowing the grenades to walk.

“Even in a post blast, as long as the safety lever is recovered we will be able to identify these tagged grenades,” an official wrote in one email.

In addition to those revelations, new evidence photos have emerged: More than 2,000 rounds of ammunition and scores of grenade parts and fuse assemblies are seen in evidence photos that were just turned over to Congress. According to Attkisson’s report, officials had taken Kingery into custody in 2010 — long before Border Patrol agent Brian Terry was murdered with a Fast and Furious-supplied gun — after having caught him trying to transport that ammunition and those grenade parts and fuse assemblies into Mexico hidden inside the spare tire of the SUV he was travelling in.

Attkisson said that ATF agents questioned Kingery at that point but then “inexplicably released” him.

Internally, some in the ATF objected to these practices. For instance, ATF’s Mexico attaché, Carlos Canino — who has cooperated with congressional investigators and appeared willingly before the House Oversight Committee last summer — said ATF was not supposed to allow weapons, including grenades, to walk.

“We are forbidden from doing that type of activity,” Canino wrote in one email. “If ICE is telling you they can do that, they are full of shit.”

This news comes on the heels of Assistant Attorney General Ronald Weich’s decision to resign his post at the Department of Justice soon. The University of Baltimore School of Law hired him as its new dean and he starts in July. Weich was the DOJ official who provided provably false information to Sen. Chuck Grassley of Iowa when Grassley began investigating Fast and Furious.

On Feb. 4, 2011, Weich wrote to Congress that the idea that “ATF ‘sanctioned’ or otherwise knowingly allowed the sale of assault weapons to a straw purchaser who then transported them into Mexico … is false.”

“ATF makes every effort to interdict weapons that have been purchased illegally and prevent their transportation to Mexico,” Weich added in that letter.

The DOJ has since retracted Weich’s letter.

Not one government official has been held accountable for Operation Fast and Furious. Scores of lawmakers — 125 House members, three U.S. senators, two governors — and many major political figures, including likely Republican presidential nominee Mitt Romney, have demanded Holder’s resignation or firing over Fast and Furious.

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