The Federal Bureau of Investigation has opened a probe into a security breach of Apple Inc's iPad that exposed personal information of AT&T Inc customers.

The FBI is aware of these possible computer intrusions and have opened an investigation to address the potential cyber threat, FBI spokesman Jason Pack said on Thursday.

AT&T acknowledged the security breach on Wednesday but said only email addresses were exposed to hackers who identified a security weakness.

It said it has corrected the flaw. It also declined comment on the FBI investigation.

(Reporting by Jeremy Pelofsky in Washington DC and Sinead Carew in New York; Editing by Bernard Orr)