DISTRICT OF COLUMBIA — A report has found that an airport biometric program is improperly gathering data on Americans, and violating their privacy.

According to a report from the Georgetown Law Center for Privacy and Technology, the Department of Homeland Security has installed facial scanners in nine international airports across the U.S., as part of their biometric exit program.

The program is part of efforts to nab travelers who are overstaying their visas, or using fraudulent documents. Passengers' faces are scanned at the boarding gate, and matched to a DHS database for verification.

Face scans are mandatory for foreign nationals, but U.S. citizens on international flights can opt out and have their documents manually checked.

It's unclear though, if American passengers are being informed of this option.

According to Homeland Security's own data, 1 in 25 travelers are erroneously rejected by the system despite using valid credentials.

The technology also reportedly had high error rates, and often inaccurately identified women and African Americans.