WASHINGTON (Reuters) - Foreign hackers targeted the computers of Mike Mullen, ex-chairman of the Joint Chiefs of Staff, the Wall Street Journal reported on Wednesday, calling it the latest in a pattern of attacks on computers of former high-ranking U.S. officials.

The FBI is pursuing the hackers, the Journal reported. The agency was not immediately available for comment.

Mullen's office confirmed that the retired admiral was cooperating with a cyber investigation.

"Admiral Mullen, now a private citizen, has responded to very specific requests and is cooperating with an ongoing cyber investigation he has been informed is focused overseas," it said in a statement.

The hackers targeted personal computers Mullen used while working on the grounds of the U.S. Naval Academy in Annapolis, Maryland, after his retirement in 2011, the report said, citing officials and others familiar with the probe.

One official said the evidence pointed to China as the origin of the hacking and that it appeared the hackers were able to access a personal email account.

A spokesman for the Chinese Embassy in Washington told the Journal he was not aware of the investigation and that his government prohibits cyber attacks.

China is often cited as a suspect in various hacking attacks in the United States and other nations. Beijing dismisses allegations it is involved.

The Journal report said current and former U.S. cyber security officials say the Mullen case is the most recent example of a series of undisclosed hacker attacks on the computer files of former senior U.S. officials.

Hackers view their computers as an easier way to get access to sensitive information, said these people, who declined to name the targeted former officials.

(Reporting By Patricia Zengerle, additional reporting by Phillip Stewart; Editing by Xavier Briand)