U.S.-Mexico border crossings account for the vast majority of escapes, said Victor Manjarrez, former chief of the Arizona Sector Border Patrol, adding that smuggling gangs take advantage of the vast desert areas to cross without being detected.

“This is a challenge for the U.S. Border Patrol because surveillance capabilities are not as robust, the terrain is rugged – making vehicle patrols difficult – and the density of Border Patrol agents is not as great “, he said.

Mr. Manjarrez added that the smuggling gangs were simply watching for “clouds of dust” produced by Border Patrol vehicles crossing the desert from miles away and hiding before agents arrived.

Escapades data is an estimate made by Customs and Border Protection based on a range of factors including CCTV footage, motion sensors, aerial surveillance, footprints and holes made in border defenses.

The figures obtained by The Telegraph have not been finalized and will be subject to adjustment under Department of Homeland Security (DHS) policy, it appears.

The DHS and Harris campaign declined to comment.