The number of fingerprint records of federal employees that have fallen into the hands of hackers is far higher than originally thought, the Office of Personnel Management (OPM) and the Department of Defense said on Wednesday.

The federal government now believes that up to 5.6 million fingerprint files were stolen from security clearance records dating back many years, Reuters reported. Originally, that figure had been put at a little over one million, the newswire recalled.

OPM serves as "a sort of human resources department for the federal government," Wired explained. The agency would not provide further details about the exact employees involved in the leak. However, it has said that data belonging to up to 21.5 million federal employees were potentially compromised by the hack, which likely originated in China, the magazine added.

The revelation comes at an awkward time, since President Barack Obama is set to host Chinese President Xi Jinping during a state visit in Washington, D.C. this week, Reuters noted. The Obama administration, which earlier this year insinuated that it might punish Beijing with sanctions over the suspected theft of U.S. trade secrets, has said that cybersecurity would be a major focus of his talks with Xi on Friday.

White House spokesman Josh Earnest, meanwhile, noted that the investigation into the data breach was ongoing. The administration did not "have any conclusions to share publicly about who may or may not have been responsible," he cautioned.

Nevertheless, the notion that the Chinese entities may have gained access to the fingerprints of millions of federal security clearance holders -- including, potentially, intelligence officers serving overseas -- is "troubling" for U.S. intelligence agencies, the Guardian assessed.

Critics in Congress accused the Obama administration of putting out the update at a time when Washington was preoccupied with the visit of Pope Francis, the British newspaper said.

"Today's blatant news dump is the clearest sign yet that the administration still acts like the OPM hack is a PR crisis instead of a national security threat," said Nebraska Republican Ben Sasse, a who sits on the Senate's Homeland Security and Governmental Affairs Committee.