Nearly one-third of the cameras in the Border Patrol’s primary surveillance system along the southern U.S. border are not working, according to an internal agency memo sent in early October, depriving border agents of a crucial tool in combating illegal migrant crossings.

Roughly 150 of the 500 cameras on watchtowers along the border have been affected nationwide, causing ‘significant impacts’ on operations according to the memo

Nearly one-third of the cameras that are part of the U.S. Border Patrol’s main surveillance system along the 2,000-mile U.S.-Mexico border are not functioning, according to an internal agency memo from earlier this month that was obtained by NBC News on Monday.