The Secret Service is looking into a “cyber breach” after what appeared to be a scan of First Lady Michelle Obama’s passport was published online.

The hacking group DC Leaks posted on its Twitter account this morning what appears to be a scanned copy of Michelle Obama’s passport, along with several White House staffers’ private communications.

The scan appeared to have been taken from a Gmail account belonging to a White House employee, a spokesman said.

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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, the hacker group which last week published personal emails from an account belonging to former Secretary of State Colin Powell’s emails, claimed responsibility for the hack.

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”.

Josh 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.”

The Secret Service, which is responsible for protecting the President and First Lady, said it was “concerned” about the apparent hacking.

“The Secret Service is concerned any time unauthorized information that might pertain to one of the individuals we protect, or our operations, is allegedly disclosed,” said communications director Cathy Milhoan.