The number of undocumented immigrants stopped at the US border with Mexico soared to more than 76,000 in February, the highest monthly level in years, US Customs and Border Protection said Tuesday.
The number of families and unaccompanied children also rose to nearly two-thirds of the total, often crossing in large groups and turning themselves into authorities to request asylum, blunting the Trump administration's tactics aimed at curbing the flow.
At 76,103, the number of people stopped at the border or detained after the crossing was up sharply from the roughly 61,000 average for the previous three months, a surprising surge for what is usually a downturn in the coldest month of the year.
It was also more than double the number of February 2018 and 3.2 times the number for February 2017, the first full month after President Donald Trump took office promising to take aim at illegal immigration.
"We are currently facing a humanitarian and national security crisis along our southwest border," said CBP Commissioner Kevin McAleenan.
"The vast increases in families and children coming across our border, in larger groups and in more remote areas, presents a unique challenge to our operations and facilities, and those of our partners."
In late January, the government launched a new policy to send the asylum-seekers -- nearly all from impoverished, crime-racked Guatemala, Nicaragua and El Salvador -- back across the border into Mexico to wait while their applications are reviewed, which can take up to two years.
But implementation of that program only began in one area of the border, at Tijuana, Mexico, and has not been put in place in other areas yet.
Meanwhile, more than 70 groups of over 100 migrants each crossed the porous border last month, handing themselves into authorities immediately.
The February surge likely included many of those who joined caravans up from Central America, people whom Trump cited to justify shutting down the government for six weeks in December and January in a bid to obtain money from Congress to build more sections of a wall along the long frontier.
When Congress still refused, Trump declared a national emergency last month that would potentially enable him to divert funds for the wall from the US military and other departments.
That move remains under legal challenge.
The number of families and unaccompanied children also rose to nearly two-thirds of the total blunting the Trump administration's tactics aimed at curbing the flow.