The number of people taken into custody along the Mexico border jumped an additional 31 percent last month as an unprecedented mass migration of families from Central America pushes unauthorized crossings to the highest levels in a decade, according to U.S. Customs and Border Protection figures released Tuesday.

Last month, the shortest of the year, was the busiest February at the border since 2007, officials said, with authorities detaining 76,103 migrants, up from 58,207 in January. The percentage of migrants who arrived as part of a family group also reached a new peak, with 40,325 parents and children taken into custody, a 67 percent leap from the previous month.

“The system is well beyond capacity and remains at a breaking point,” Customs and Border Protection Commissioner Kevin McAleenan, the nation’s top border security official, told reporters Tuesday afternoon.

The unchecked increases in border crossings are likely to aggravate the increasingly strident debate between supporters of President Trump’s wall-building plan and critics of his administration who have resisted White House attempts to enact tougher enforcement measures.

The February statistics are the clearest indication yet that unauthorized migration remains on a sharp upward trajectory after a historic low point in 2017. Department of Homeland Security officials are bracing for an even bigger surge this spring.

McAleenan said his agency had apprehended and processed more families in the first five months and five days of the 2019 fiscal year than during all of fiscal 2018.

“The situation is not safe for migrants,” he said. “It challenges our ability to provide humanitarian care. It contributes to dangerous conditions on our border and enables smuggling while enriching criminals.”

“Regardless of anyone’s preferred policy outcome, the status quo is unacceptable,” Mc­Aleenan said. “It presents an urgent and increasing crisis.”

Across the U.S.-Mexico border, Customs and Border Protection agents are grappling with huge numbers of Central America migrants seeking asylum. (Jorge Ribas/The Washington Post)

An attractive job market in the United States is prompting more Central Americans to leave the poverty and insecurity of their home countries and head north, typically in groups of one parent and one child. Such pairings all but ensure the family will be processed quickly and released from U.S. custody in a matter of days.

“We know what is driving these trends,” McAleenan said. “These increases in traffic are a direct response from smugglers and migrants to the vulnerabilities in our legal system.”

A backlog of more than 800,000 pending cases in U.S. immigration courts and court-imposed limits on the government’s ability to quickly detain and deport the family groups have become “the most significant factors affecting border security,” McAleenan said.

During a month when many families arrived with flu symptoms and other illnesses, U.S. agents have been increasingly pulled away from the border to escort families to hospitals, said Brian Hastings, the Border Patrol’s chief of operations.

Border Patrol agents are on track to make 31,000 medical referrals this fiscal year, Hastings said, up from 12,000 last year. Hastings said the Border Patrol is dedicating 25 to 40 percent of its manpower “to the care, transportation and the humanitarian mission.”

Hastings said the Border Patrol has documented at least four recent incidents in which smuggling groups attempted to sneak drugs across the border while U.S. agents were overwhelmed by the arrival of a large group of migrant families.

The groups, the biggest totaling more than 300 parents with children, have been showing up at remote border locations with few U.S. personnel and little infrastructure.

In December, two Guatemalan children died in CBP custody after crossing in the El Paso sector. McAleenan said Tuesday his agency is moving forward with plans to build a new processing center there for families and children to alleviate the humanitarian emergency.