Apple says that some celebrity accounts were deliberately targeted and hacked, leading to the posting of nude photos online.
The company says its investigation found that individual accounts had been compromised with a "very targeted attack" on user names, passwords and security questions.
But Apple said in a statement there wasn't a general breach involving its systems, including the iCloud and Find my iPhone services.
The FBI said Monday that it was addressing allegations that online accounts of several celebrities, including Oscar-winner Jennifer Lawrence, had been hacked, leading to the posting of their nude photographs online.
The FBI did not say what actions it was taking to investigate who was responsible for posting naked photos of Lawrence and other stars. Apple said at the time it was looking into that. Tuesday afternoon's statement was the first confirmation from Apple that accounts had been hacked.
Apple said it was still working with law enforcement “to help identify the criminals involved.”