A group of cybercriminals hacked into data systems at insurance company Aflac, possibly gaining access to sensitive information such as Social Security numbers and health reports, the company said on Friday.

Aflac, which provides supplemental insurance to around 50 million individuals whose expenses are not covered by their primary providers, said it was not yet known how many customers are affected by the data breach but that the personal data includes customers' claims,

Aflac recently revealed that hackers stole its customers' data in a cyberattack. Details remain scarce, but the company says it "was caused by a sophisticated cybercrime group" that's targeting the insurance industry.