The U.S. Postal Service said Monday morning that it was hacked. While they began investigating the cyber security intrusion, they said information from employees were compromised. It also affected information from customers.

Information stolen related to employees include names, birthdates, Social Security numbers, addresses and emergency contacts, USPS said. Hackers also obtained the dates employees started and ended at USPS.

When it comes to customers, those affected are anyone who called the USPS Customer Care Center from Jan. 1 to Aug. 16 either by phone or email. The hackers obtained names, addresses, email addresses, telephone numbers and other information a customer provided. However, USPS says that, “We do not believe that potentially affected customers need to take any action as a result of this incident.”

According to The New York Times, the statement came just weeks after the White House confirmed that unclassified computers there were hacked. The White House believes that the culprits in that attack were Russian, while the USPS attack could be from Chinese hackers. Of course, this is difficult to confirm, but if it was Chinese hackers, the question becomes what were they looking for.

The USPS’ inspector general told the agency of the breach in mid-September, so it’s not known why they waited so long to announce that the breach happened. An official told CNN that the breach may have affected as many as 750,000 employees.