The number of apprehensions and denials of people attempting to enter the U.S. via the southern border spiked in March, according to federal data released Tuesday.
Data from U.S. Customs and Border Protection (CBP) showed that 92,607 people were apprehended after crossing the border between ports of entry in March, compared to 66,884 the previous month.
Tuesday's numbers marked the highest one-month total of apprehensions so far this fiscal year.
The largest surge among groups of migrants was among "family units," or groups of migrants traveling with children, according to CBP. The number of apprehensions of family units rose from 36,531 in February to 53,077 in March.
CBP breaks down apprehensions into three categories: family units, unaccompanied alien children (UACs) and single adults.
Family unit apprehensions started ticking up last August, but UAC and single adult numbers had remained more or less stable throughout the 2018 and 2019 fiscal years.
Though family unit apprehensions showed the greatest increase so far — apprehensions of people traveling as families have gone from 4,836 in October 2017 to 53,077 in March 2019 — UAC and single adult numbers also rose significantly last month.
Authorities apprehended 30,555 single adults who crossed the border illegally last month, compared to 23,525 a month prior. That number had hovered around 20,000 a month for the past two fiscal years.
CBP and Border Patrol also apprehended 8,975 children in March, compared to 6,828 in April. The March figure was the single largest UAC apprehension figure since December of 2016.
Northward migration over the past two years has been driven by a number of factors, including violence and economic instability in the Northern Triangle of Central America, composed of Honduras, Guatemala and El Salvador.
Specific local circumstances have shifted the proportion of people coming from each country over time.
A drought in northern Guatemala drove a significant increase in asylum-seekers from that country, while a stable democratic transition in El Salvador seems to have pushed that country's numbers down, despite persistent criminal activity and economic stagnation.
Apprehensions have also been driven up by changes in migrant behavior, as a larger proportion of people who cross the border are giving themselves up to authorities to claim asylum in the United States.
A spokesman for the Department of Homeland Security did not immediately return a request for comment on the rise in border apprehensions.
News of the surge in apprehensions comes two days after the ouster of Homeland Security Secretary Kirstjen NielsenKirstjen Michele NielsenFar-left bullies resort to harassing, shaming Kyrsten Sinema — it won't work Ex-Trump official: 'No. 1 national security threat I've ever seen' is GOP Left-leaning group to track which companies hire former top Trump aides MORE. During her tenure, the embattled Homeland Security Department chief oversaw the Trump administration's response to a surge in immigration at the southern border, including the administration's controversial "zero tolerance" immigration policy.
Updated at 4:05 p.m.