As criticism of the Biden administration's handling of the Mexican border mounts, the number of migrants reaching the border has risen to a 20-year high, according to new figures from US Customs and Border Protection (CBP).

According to statistics released Thursday by CBP, in May a total of 180,034 people attempted entry at the border - up slightly from the 178,854 recorded in April and 172,000 recorded in March.

The figure is believed to be the highest recorded monthly total since 2000.

The number of unaccompanied children and single minors from the Northern Triangle countries, however, fell by 23%, with 10,765 encounters, compared to 13,940 in April. Encounters of family units from the region also fell by 31% from 32,674 in April to 22,630 in May 2021.

Harris in Mexico: from AMLO to the Sun Belt

These declines, however, were offset by an increasing number of single adult migrants, of whom 121,082 were apprehended last month.

In a statement, CBP also said that the - largely as a result of the pandemic - a "larger-than-usual" number of non-citizens making multiple border crossing attempts "and means total encounters somewhat overstate the number of unique individuals arriving at the border." 

The number of unaccompanied children and single minors from the Northern Triangle countries, however, fell by 23%, with 10,765 encounters, compared to 13,940 in April. Encounters of family units from the region also fell by 31% from 32,674 in April to 22,630 in May 2021

Officials said that the new data also includes a large amount of migrants - approximately 40,000 - from nations other than Mexico and Central America, including Cubans, Haitians, Ecuadorans, Brazilians and citizens of various African nations.

The data shows that 38% of May 2021 encounters were with individuals who has at least one prior encounter in the previous 12 months, compared to an average one-year re-encounter rate of 15% between 2014 and 2019.

CBP published the data a day after Vice President Kamala Harris concluded a trip to Guatemala and Mexico, part of a wider effort to reduce the flow of migrants at their source countries.

During the visit, Harris issued a warning to migrants, urging them to reconsider any plans to head to the border.

"Do not come," she said. "You will be turned back."

The new figures also come as the Biden administration - and Harris in particular - have come under intense criticism from political opponents, who continue to fault Harris for not visiting the border in person. 

The data shows that 38% of May 2021 encounters were with individuals who has at least one prior encounter in the previous 12 months, compared to an average one-year re-encounter rate of 15% between 2014 and 2019.

In a written opinion piece on Thursday, for example, Florida Republican congressman Carlos A. Giménez said that Harris has been "missing in action" since being appointed by President Biden to oversee efforts to control the border.

"It is as if Harris believes this issue will magically disappear if we pretend it is not there, refusing to visit the border or even holding a press conference on the crisis," she said. "Instead, she tries to laugh it off while the crisis only gets worse."

Ahead of Vice President's Latin America trip, immigration takes center stage as domestic issue

The issue of immigration and the border has become an increasingly important issue to US voters, many of whom disapprove of the government's handling of the issue.

AP

Recent statistics from Pew Research show that nearly 70% of US voters believe that the government is doing a very (33%) or somewhat (35%) bad job dealing with the increased number of people seeking asylum at the country's southern border.

Only 29% said they believed the government is doing a very or somewhat good job.

The statistics also show a significant partisan divide about the issue, with 78% of Republicans saying it is important to make it more difficult for asylum seekers to be granted legal status in the US, compared to 39% of Democrats.

While 79% of Democrats say it is very or somewhat important to increase aid to Central American countries, where many asylum seekers come from, only 40% of Republicans say the same.