An image purported to be a scanned copy of American first lady Michelle Obama’s passport has been published online alongside personal emails said to belong to a low-level White House staffer who worked with Hillary Clinton’s presidential campaign.
The scan appeared to have been taken from a Gmail account belonging to a White House employee, a spokesman said.
Other confidential information was published online, including travel details, names, social security numbers and birth dates of members of staff.
The White House said it had not yet verified the documents.
DCLeaks.com, a hacker group which last week published personal emails from an account belonging to former US Secretary of State Colin Powell’s emails, claimed responsibility for the hack.
The US attorney general, Loretta Lynch, said the incident was “something that we are looking into”. White House press secretary Josh Earnest said the breach “should be a wake-up call for all of us”.
Mr Earnest said that the employee targeted by the hackers was a contract worker and not a permanent member of staff.
He said: “At this point I cannot announce any sort of conclusion that’s been reached about the individual or individuals that may have been responsible for the cyber breach that resulted in this information being leaked.”
And on Friday, internet giant Yahoo confirmed that hackers stole information from about 500 million users in 2014, in what appears to be the largest publicly disclosed cyber-breach in history.