San Bernardino Shooter's iPhone Doesn't Yield 'Smoking Gun' Despite Battle Over Encryption

— -- The FBI has finally accessed an iPhone belonging to one of the San Bernardino shooters last month but the device hasn't yielded a "smoking gun," according to law enforcement sources who said authorities are continuing to follow leads generated by the device.

The iPhone 5c used by Syed Farook did not contain any identities of suspected co-conspirators or overseas contacts that investigators believe may be related to the attacks, law enforcement sources told ABC News.

Federal officials announced last month they successfully cracked into an iPhone belonging to one of the San Bernardino shooters and were no longer pursuing legal action to compel Apple to help unlock the device.

The method used to access the device and the identity of the third party who helped are unknown. FBI Director James Comey said earlier this month the tool purchased from a private party and used to access Farook's iPhone only works on a "narrow slice" of phones, such as the iPhone 5c running iOS 9.

Apple has been staunch in its position that creating a backdoor for government officials would undermine the security of millions of users.