Hackers took millions of fingerprints during the massive breach at the U.S. Office of Personnel Management (OPM) that took place early this year. This was only revealed in a statement released by OPM Wednesday, which highlighted the extent of personal information stolen from at least 22 million federal workers, job applicants, including those of their families.

Around 5.6 million fingerprints were reportedly stolen, which is five times more than what was initially thought, the Voice of America reported. It is still unclear how the hackers will use the fingerprints but officials say its utility could be limited at present.

"However, this probability could change over time as technology evolves," OPM said in the report.

Aside from the fingerprint data, the unprecedented cyber heist also took Social Security numbers and addresses among other important personal information of former and current federal employees. What is particularly disturbing about the fingerprint theft was the nature of the data exposed. Unlike passwords or the Social Security numbers, the fingerprints cannot be replaced or erased, notes the Washington Post.

American intelligence agencies identify China as the culprit behind the cyber attack, according to the New York Times. Officials, however, will not confirm this in public. It is, however, an issue that will sure to crop up in the dialogue between President Obama and the visiting Chinese President Xi Jinping later this week.

The success and efficacy in the manner by which the hack was carried out is astonishing. This is highlighted in the way it was only brought to light because of a scheduled updating of equipment and systems at OPM, HNGN previously reported. The hacking began several years earlier.

For more on the U.S./China cyber peace deal, click here.