Data: The number of migrants apprehended at the U.S.-Mexico border in March is highest in 15 years Unaccompanied minors hits all-time high in March, records show Published: Tags: . (Henry Keller/KSAT) In March, Border Patrol agents encountered more migrants in a single month than they have since 2006, according to the latest numbers provided by U.S. Customs and Border Protection. According to the latest data available from U.S. Customs and Border Protection (CBP), Border Patrol agents logged 172,331 apprehensions in March along the U.S.-Mexico border. That’s a 71% increase from February, when 101,028 were reported. Spring months are generally the highest of the year for crossings.