Almost 400 asylum seekers have been arrested in Arizona after tunnelling under the US-Mexico border, officials have said.
The central American migrants, mostly made up of families, were detained by US Customs and Border Protection (CBP) after handing themselves in near the city of San Luis.
Authorities said the 376-strong group, which was almost entirely from Guatemala and included 176 children, made no effort to evade immigration agents.
They made their way into the US by digging shallow holes under a steel barrier about 10 miles east of a border crossing in San Luis, which has become a major route for migrants in recent years.
Despite steel plates being welded to a barrier of bollards in a bid to prevent illegal crossings by people in vehicles, they have not provided much of a deterrent to those travelling on foot.
Border Patrol spokesman Jose Garibay III said there was no concrete footing to prevent digging and that the group had been able to dig multiple holes without much difficulty so that everyone could get across quickly.
CBP has only just released photos and videos of the migrants waiting in the desert despite being arrested on Monday, and they have since been taken to Yuma.
Anthony Porvaznik, a chief CBP officer in the city, told ABC News that 87% of the illegal migrants apprehended there were families with children.
He added: "In my 30 years with the Border Patrol, I have not been part of arresting a group of 376 people. That's really unheard of."
CBP has come under scrutiny recently over their treatment of migrants in detention, with two children having died while in custody in the weeks leading up to Christmas.
Two days after the detentions in Yuma, a group of 247 people from Central America gave themselves up to border officials in New Mexico.
President Trump addresses the nation over immigration and the border wall 1:05
Another group of 115 were found in the same area on Thursday, again featuring large numbers of Guatemalans.
More are on their way, with hundreds of Honduran migrants crossing over the border into Guatemala this week in the hope of reaching the US.
The caravan of people made its way peacefully, with those on-board showing their documents to security personnel under the watchful eye of 200 Guatemalan police and soldiers.
Despite the likelihood of arrest and an increasingly hostile rhetoric from the White House as President Donald Trump seeks funding for his proposed southern border wall, people still seek to enter the US illegally.
But while there has been a surge in the number of Central Americans seeking asylum in the US in recent months, the number of arrests remains low by historical standards.
There were 396,579 arrests on the Mexican border in the 2018 financial year, an increase of 30% on a 46-year low during the same period a year earlier - but still well below a high of more than 1.6 million in 2000.
