More than 143 million Americans may be affected after hackers stole data from Equifax, one of three major consumer credit reporting agencies.

According to the Washington Post, the personal data contained Social Security numbers, birth dates and home addresses.

Equifax also lost control of an unspecified number of driver’s license numbers, credit card numbers for 209,000 customers and credit dispute documents for 182,000 customers.

Equifax Chairman and CEO, Rick Smith, says they discovered the hackers had gained access to certain data files on July 29, and the unauthorized access occurred between mid May and July.

Smith also says Equifax immediately took action, contacting law enforcement and meeting with a cyber security firm.

The company said Thursday that it was alerting all affected customers by mail. In addition, a website has been established, equifaxsecurity2017.com,  to help customers understand the breach and check whether they were affected.

The company declined to comment about which Web application was hacked nor specify why it waited six weeks to alert consumers.