After Chinese hackers reportedly carried out a huge cyber attack, millions of US government workers are at risk.
The Office of Personnel Management (OPM) confirmed that almost four million current and past employees have been affected due to the massive breach, which could also affect every federal agency, reported the BBC.
Though Susan Collins, a member of the Senate Intelligence Committee, said that the violation was believed to be carried out from China, the Chinese embassy in Washington has warned not to "jump to conclusions".
Spokesman Zhu Haiquan told Reuters news agency that the accusations were "not responsible, and counterproductive".
OPM is the human resource department for the federal government and assembles records of all federal government employees including employee job assignments, performance reviews and training.
It had detected a cyber-invasion in April 2015 with help of a new cyber security system known as Einstein. The FBI said it was investigating the breach.
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The officials said that the breach did not involve background checks and clearance investigations.
Collins called the breach "yet another indication of a foreign power probing successfully and focusing on what appears to be data that would identify people with security clearances."
Ken Ammon, chief strategy officer of cyber security firm Xceedium warned that the hacked data could be used to impersonate or blackmail federal employees with access to sensitive information.
Meanwhile, Congressman Adam Schiff has requested for cyber databases to be upgraded following the most recent attack.