(Reuters) -Insurer Aflac said on Friday it identified suspicious activity on its network in the United States on June 12.

The company said it has reached out to third-party cybersecurity experts to investigate the incident and has commenced a review of potentially impacted files.

These files contain personal information of its customers, including social security numbers and health-related details, it added.

Shares of Aflac ( AFL ) fell 1.6% in premarket trading.