media captionNew footage reveals crowded child migrant facility

The number of undocumented migrants reaching the US-Mexico border has hit the highest level in more than 20 years in the latest sign of the humanitarian crisis facing the Biden administration.

US Customs and Border Protection (CBP) said it caught 180,034 migrants, mostly single adults, in May.

The number was up slightly from 178,854 in April and 172,000 in March.

It was the biggest monthly total since April 2000 with increasing numbers coming from outside Central America.

This include countries like Ecuador, Venezuela, Cuba, Haiti and even some African nations.

The number of unaccompanied children from Central America dropped to 10,765 in May, compared with 13,940 the previous month, according to CBP figures.

The agency said that of the 180,034 people encountered in May, 112,302 individuals were expelled under a Trump-era policy known as Title 42, which was kept in place by US President Joe Biden.

The border agency said the average daily number of children in its custody has plummeted to 640. However, another 16,200 migrant children are being held by the US health department.

image copyrightGetty Imagesimage captionMs Harris holds talks with the Guatemalan president on Monday

Some of these children have no relatives in the US, Health Secretary Xavier Becerra said on Tuesday in congressional testimony.

JooYeun Chang, a US health department acting assistant secretary, said the numbers of unaccompanied migrant children since March are "simply unprecedented".

The CBP update follows US Vice-President Kamala Harris' two-day visit to Guatemala and Mexico to address the root causes of immigration. She told illegal immigrants thinking of making the trek to America: "Do not come."

Harris under pressure to visit US-Mexico border

According to CNN, the White House was "not thrilled" by Ms Harris' testy exchange during the trip with a TV news anchor, who asked her why she had not herself visited the US-Mexico border.

The cable network's White House correspondent John Harwood said the vice-president's "obvious discomfort" with the question by NBC and her "nervous laughter" had left the White House "confused".

  • What is Biden doing differently at US border?

Mr Biden campaigned on the promise of a more humane immigration agenda. Since coming into office, the Democratic president has ended construction of the border wall and repealed Mr Trump's Remain in Mexico policy, which required US asylum seekers to wait in Mexico while their applications were processed.

image copyrightGetty Imagesimage captionA man detained in Arizona wears a T-shirt saying "please let us in"

He has also urged Congress to create a path to citizenship for the millions of illegal immigrants already in the US.

A recent Biden administration memo requires US Immigration and Customs Enforcement officers to seek authorisation from senior managers before seeking to deport certain migrants, according to the Washington Post, a policy that the newspaper predicted would result in a steep decline in immigration arrests and deportations.

Republicans have blamed Mr Biden's policies for the border surge, and so did Guatemalan President Alejandro Giammattei, on the eve of his meeting with the US vice-president.

He told CBS News on Sunday that after Mr Biden took office "the very next day the coyotes were here organising groups of children to take them to the United States".