The FBI is investigating a hacking attack that forced the U.S. State Department to disable part of its email system and may be linked to a previously disclosed intrusion of the White House network.

The FBI on Monday said it opened investigations into the State Department attack, as well as a separate hack on the Postal Service.

¡°We are aware of these reports and are working with our interagency partners to investigate the matter,¡± FBI spokesman Joshua Campbell said in an email. He declined comment on any link between the State Department and White House attacks.