Automated license plate recognition (ALPR) technology uses cameras to identify cars, alert police departments if they match a license plate on a “hot list,” and track their movements.

“In support of its public safety focus, ICE, consistent with other law enforcement agency practice, is exploring the ability to obtain access to a National License Plate Recognition database—allowing officers and agents to identify subjects of ongoing criminal investigations,” Gillian Christensen, a DHS spokesperson, told Ars Technica. “The database could only be accessed in conjunction with ongoing criminal investigations.”

DHS has distributed more than $50 million in federal grants since 2007 to law-enforcement agencies for ALPR technology. Thousands of police departments across the country use the scanners.