WASHINGTON (AP) — FBI officials could have tried harder to unlock an iPhone as part of a terrorism investigation before launching an extraordinary court fight with Apple Inc. in an effort to force it to break open the device, the Justice Department's watchdog said Tuesday.

The department's inspector general said it found no evidence the FBI was able to access data on the phone belonging to one of the gunmen in a 2015 mass shooting in San Bernardino, California, as then-FBI Director James Comey told Congress more than once. But communications failures among FBI officials delayed the search for...