Top officials at the Clinton Foundation believe the organization was hacked — causing concern that the data breach will show Hillary Clinton and State Department staff giving preferential treatment to top donors.

No message or document from the New York-based Clinton Foundation has surfaced yet in public.

But the foundation has hired the security firm FireEye to examine its data systems after seeing indications they might have been hacked, sources told Reuters.

The Clinton Foundation has been scrutinized for accepting foreign donations and after it was revealed certain top-level donors got preferential treatment at the State Department.

And the suspected hack has left some Democrats and Clinton campaign officials worried that cyber-infiltrators might have obtained emails and voice messages that could be used to bolster allegations that donors to the Clinton Foundation were rewarded with access to Clinton and her aides while she was secretary of state, or to her husband, former President Bill Clinton.

Neither former White House counsel Kathryn Ruemmler, the Clinton Foundation’s principal lawyer, nor a spokeswoman for the foundation responded to requests for comment on the hacking and the precautions the organization has taken. Officials with FireEye said the company could not discuss its clients.

US officials said the hackers used the same techniques Russian intelligence agencies or their proxies employed against Democratic Party groups, which suggests that Russians also attacked the foundation.

Kremlin officials dismissed as absurd the allegations of Moscow’s involvement, which were made last month amid political party nominating conventions for the Nov. 8 election.

Rep. Jim Himes, a Democrat on the House intelligence committee, said the United States should carry “a big stick” in cybersecurity matters.

“The US government needs to be very clear, very direct, and hold these people accountable.”

With Post wires