The U.S. Customs and Border Protection (CPB) disclosed earlier today that hackers have breached a database of travelers photos and license plates, according to the Washington Post. The agency declined to say how many people might have had their images stolen from the subcontractor that held them.

The CPB processes nearly 400 million travelers at ports of entry annually. In light of the fact that the CPB has been building an extensive photo database as part of its growing facial-recognition program, the privacy implications of this breach for American citizens and visitors could be grave.

"This breach comes just as CBP seeks to expand its massive face recognition apparatus and collection of sensitive information from travelers, including license plate information and social media identifiers," said American Civil Liberties senior legislative counsel Neema Singh Guliani in a statement. "This incident further underscores the need to put the brakes on these efforts and for Congress to investigate the agency's data practices. The best way to avoid breaches of sensitive personal data is not to collect and retain such data in the first place."