The USA informed that the personal financial data of up to four million current and former government officials may have been breached by a cyber attack reportedly originating from China.

Credit card data, banking records and other forms of financial information could have been stolen in the attack, USA Today reports.

Earlier on Thursday, it was reported that the US government secretly expanded the warrantless surveillance of the internet traffic to combat hacking from overseas.

The Federal Bureau of Investigation (FBI) is investigating the latest hack, saying it will continue to investigate and hold accountable those posing threat to cyberspace.

The Office of Personnel Management, which conducts background checks for security clearances, is informing the affected government officials.

According to some reports, which have not been confirmed yet, security clearance forms were taken in the data breach.

The affected individuals are advised to monitor their financial account statements and immediately report any suspicious or unusual activity to the relevant institutions.

This is the latest in a series of data breaches, but could be the worst one due to the large number of people affected in the attack.