The number of families trying to cross also has surged, with more than 12,500 people caught — a 173 percent increase over last year. The family surge underscored the changing nature of the flow of migrants, with parents increasingly risking the journey with young children in tow, hoping to take advantage of what they believe are lenient deportation policies under President Obama.

Migration usually surges in the spring then drops in the summer and remains low through the winter. This year has defied that trend, leaving the Obama administration scrambling to rejuvenate its capacity to handle a problem that Homeland Security officials hoped was behind them.

“We continue to aggressively work to secure our borders, address underlying causes and deter future increases in unauthorized migration, while ensuring that those with legitimate humanitarian claims are afforded the opportunity to seek protection,” U.S. Customs and Border Protection said in a statement.