According to the FBI, only the iPhone 5c running iOS 9 can be unlocked by the tool the U.S. gonverment used to crack the iPhone used by one of the San Bernardino killers. The tool does not work on the iPhone 5s or 6, Federal Bureau of Investigation director James Comey said onWednesday at Kenyon College.

Comey added that the government hasn's decided yet whether it would disclose to Apple the flaw that aided the hack.

A court in California ordered Apple to help the FBI to hack the passcode of the iPhone 5c. The FBI was concerned that, if an auto-erase feature was activated on the phone, the data would be automatically erased after 10 unsuccessful attempts, so it asked for a workaround from Apple.

The FBI later said it had gained access to the data and the court vacated the order on Apple.

The agency has to date not disclosed the name of the organization or the hack that was used.

Apple had refused to help the FBI create a "backdoor" in its operating system.