The number of people taken into custody along the Mexico border jumped another 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.

Border Patrol Agent Ramiro Cordero puts arm bands on Mairon Argueta and his daughter Elsi Argueta, 4, of Honduras, while they are wrapped in mylar blankets in El Paso, Texas, on Feb. 22. Washington Post photo by Carolyn Van Houten

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

“The system is well beyond capacity and remains at a breaking point,” CBP 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 Donald 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 from a historic low point in 2017. Homeland Security officials are bracing for an even bigger surge this spring.

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

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

Border Patrol agents load migrant families wrapped in mylar blankets into a transport van to take them to a nearby holding facility in El Paso, Texas, on Feb. 22. U.S. officials say the number of people taken into custody at the border has surged. Washington Post photo by Carolyn Van Houten

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

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 assure the family will be quickly processed 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 the hospital, 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 percent to 40 percent of its manpower “to the care, transportation and the humanitarian mission.

“They’re being pulled from the national security mission to do these things,” he said, calling the situation “unsustainable.”

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, Texas, 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.