CBS: "Secret recordings raise new questions in ATF 'Gunwalker' operation"

Has the Obama administration been caught hiding evidence in the "Gunwalker" case? From CBS:

CBS News has obtained secretly recorded conversations that raise questions as to whether some evidence is being withheld in the murder of a Border Patrol agent.
(Scroll down to listen to the audio)
The tapes were recorded approximately mid-March 2011 by the primary gun dealer cooperating with ATF in its "Fast and Furious" operation: Andre Howard, owner of Lone Wolf Trading Company in Glendale, Arizona. He's talking with the lead case ATF case agent Hope MacAllister.
The tapes have been turned over to Congressional investigators and the Inspector General.

As CBS News first reported last February, the Bureau of Alcohol, Tobacco, Firearms and Explosives allegedly allowed thousands of weapons to "walk" onto the streets without interdiction into the hands of suspected traffickers for Mexican drug cartels in its operation "Fast and Furious."

The conversations refer to a third weapon recovered at the murder scene of Border Patrol Agent Brian Terry.

Agent: I was ordered to let guns into Mexico

Court records have previously only mentioned two weapons: Romanian WASR "AK-47 type" assault rifles. Both were allegedly sold to suspects who were under ATF's watch as part of Fast and Furious.

Also, a ballistics report turned over to Congressional investigators only mentions the two WASR rifles. The ballistics report says it's inconclusive as to whether either of the WASR rifles fired the bullet that killed Terry. . . .