Growing CarrierIQ controversy: Why did the FBI turn down FOIA request?

Well, well, it looks like someone's hiding some truth behind the curtains.  According to ComputerWorld, the FBI has turned down MuckRock's / Michael Morisy's Freedom of Information Act (FOIA) requests regarding its use of CarrierIQ software, specifically:

Any manuals, documents or other written guidance used to access or analyze data gathered by programs developed or deployed by Carrier IQ. Please query any departments or groups that routinely work with mobile and wireless carriers in monitoring, deciphering, intercepting or otherwise accessing electronic communications.

 In response, an FBI section chief replied that Morisy's request was denied:

I have determined that the records responsive to your request are law enforcement records; that there is a pending or prospective law enforcement proceeding relevant to these responsive records; and that release of the information contained in these responsive records could reasonably be expected to interfere with the enforcement proceedings.

Well that's downright scary, and it appears to be potential proof that CarrierIQ has not been entirely truthful about what its software is capable of.  And what coincidence that CarrierIQ has just put out a pdf report on what it is and isn't doing.

So who are you going to trust: the company that denies collecting private information, or the FBI that is citing private information being collected in ongoing criminal investigations, via CarrierIQ software?

Just two months ago, we were facing the possibility of our government allowing itself to lie about FOIA requests.  Fortunately they abandoned that idea a week later.  So if it comes down to truth-telling, I'm more likely to believe the FBI with its mucky prosecution shield, than CarrierIQ who is currently being sued by individuals and investigated by the FTC.