The southwest border saw a significant jump last month in apprehensions and denials of people attempting to enter the United States, according to data released Tuesday.

U.S. Customs and Border Protection (CBP) data shows that 66,450 people were apprehended after crossing the border between ports of entry in February, compared to 47,986 the previous month.

A further 9,653 people were turned away at ports by U.S. border agents last month, a slight decrease from the 10,309 turned away in January.

ADVERTISEMENT The sharp increase in apprehensions was led by a continuing upward trend in crossings by family units, according to figures released by the administration.

Of the 66,450 people apprehended in February, 36,174 were traveling as family units — composed of adults and children traveling together — and 6,825 were unaccompanied children.

In January, border authorities apprehended 24,189 people in family units and 5,119 unaccompanied children.

CBP officials said in a statement that the family units and unaccompanied children apprehended at the border are predominantly Central American.

"We have apprehended and encountered more families in just five months and five days than last year's record total. Not only are the numbers increasing, the percentage of people from the Northern Triangle of Central America has increased as well," CBP Commissioner Kevin McAleenan said in a press conference Tuesday.

McAleenan added that 70 percent of crossings are from people from the Northern Triangle, and 62.5 percent of crossers are vulnerable families and children.

He also warned that criminal groups are using the large groups as bait to distract agents from surreptitious illicit activity on the border.

Over the past decade, illegal crossings by Mexicans have consistently dropped, giving way to Central American migrants escaping violence and economic distress in the region.

"Unlike historical crossings, which are comprised in a large majority of single adult males from Mexico, who could be repatriated quickly, families and children from Central America require increased care and processing, and are released into the United States, pending adjudication of their immigration claims," McAleenan said.

He also noted that migrants are increasingly traveling in large groups - known as caravans — rather than individually trying to sneak into the United States.

Central American family units tend to travel in caravans both for safety and to reduce the amount of money they pay human smugglers.

In fiscal 2019, which started in October, Border Patrol has encountered over 70 large groups — defined as a group of more than 100 individuals — which accounted for 12,069 apprehensions.

The previous record for large group apprehensions was in fiscal 2018, when Border Patrol encountered 13 large groups.

Those large groups have increasingly chosen remote areas to cross the border before turning themselves in to Border Patrol agents, taking advantage of laws that allow anyone to file asylum applications once in U.S. territory.

The shift in migration patterns has strained CBP's resources, as the agency was created to deal with single adults from Mexico.

Border apprehension and inadmissibility numbers are generally used as an indicator of total illicit crossing attempts.

It's unclear to what extent the higher numbers are due to a sustained increase in migrants fleeing Central America, or if the data are skewed by the behavioral changes of migrants, such as traveling in caravans and generally surrendering to authorities rather than sneaking in.

And, because the caravans group large numbers of asylum seekers, the surges could be temporary.

More migration graphics. Note the big jump in arrivals from #Honduras. My guess: participants in mid-January "caravan" from SP Sula who got humanitarian visas while in #Mexico. If that's it, then Honduran arrivals will decrease in March, as Mexico stopped giving visas in-country. pic.twitter.com/XgmujtF0IH — Adam Isacson (@adam_wola) March 5, 2019 Both the Trump administration and migrant-rights activists attribute the spike to the change in Northern Triangle migration patterns, but they differ as to whether the apprehension and inadmissibility numbers show an overall increase in immigration from Mexico and Central America. Adam Isaacson, a Latin American security expert at the Washington Office on Latin America (WOLA), tweeted that Honduran migration could drop in March, as Mexican authorities have stopped giving transit visas to Honduran nationals already in-country.Both the Trump administration and migrant-rights activists attribute the spike to the change in Northern Triangle migration patterns, but they differ as to whether the apprehension and inadmissibility numbers show an overall increase in immigration from Mexico and Central America.

"This increased flow presents, currently at our highest levels in over a decade, both a border security and humanitarian crisis, challenges our resources and personnel, and is negatively impacting border security," McAleenan said.

Doug Rivlin, a spokesman for progressive immigrant-rights group America's Voice, said overall numbers are still at historical lows, and that asylum seekers should not be counted as illicit border crossers, since asking for asylum is not illegal.

"Despite all of Trump’s hype on caravans and marauding criminal hordes, the reality is that overall numbers of people coming to the U.S.-Mexico border without visas remains at historically low levels," said Rivlin.

—Updated at 5:42 p.m.