More than 144,000 undocumented immigrants crossed the United States' southern border with Mexico in May, the largest monthly total in 13 years, Border Patrol officials said Wednesday.
Of those encountered by Border Patrol officers, 132,000 failed to present themselves at legal ports of entry, according to Customs and Border Protection officials.
Border Patrol officials have struggled to handle an influx of Central American migrants crossing the border, as thousands flee from political and economic instability.
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"We are in a full-blown emergency, and I cannot say this stronger: The system is broken," said acting CBP Commissioner John Sanders.
President Donald Trump has threatened to levy a 5%, and later 25%, tariff on Mexican imports unless the Mexican government increases efforts to stop migrants crossing into the U.S.