LONDON-Images of tens of thousands of people crossing the US border with Mexico have been stolen in a major hack, the US Customs and Border Patrol (CBP) has said. The breach, which affected the network of a sub-contractor, also saw photos of vehicle licence plates stolen, said the CBP.

It said fewer than 100,000 people were affected based on “initial reports”.

It also contradicted claims that image data had been shared on the dark web.

“CBP has alerted Members of Congress and is working closely with other law enforcement agencies and cyber-security entities... to actively investigate the incident,” it added.

CBP uses cameras at airports and land border crossings as part of a growing facial-recognition programme designed to track people entering and exiting the US.

The agency said the sub-contractor in the breach had stored the images on its systems without official consent, and that CBP’s own systems were not affected. The pictures were of people in vehicles entering and leaving the country via a single border entry point, which CBP did not name.

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It said that no other identifying information - such as passport data or other travel document photos - had been compromised. In late May, technology news website the Register reported that images of licence plates belonging to vehicles passing through CBP checkpoints had been shared on the dark web.