There are fears of chaotic scenes on the US-Mexico border when a rule known as Title 42 expires on Thursday night.
The emergency law was introduced in 2020 under former US president Donald Trump and was officially aimed at keeping migrants with COVID-19 out of the US. In reality, it became an easy way of avoiding asylum claims.
With the end of the pandemic, Title 42 is to be scrapped. But it is being replaced with new policies that some fear will make attempts to enter the US even more difficult.
"They say that after the 11th we won't be able to go in," said Wiljen Díaz, a migrant from Venezuela. "That's why people are in such a hurry. No one can say for sure, but we have to get ahead of things."
Migrants will have to make an appointment to apply for asylum through an application. If they fail to do so, they could be deported and banned from entering the country for five years.
On Wednesday, the US Homeland Security Department announced a rule to make it extremely difficult for anyone who travels through another country, like Mexico, to qualify for asylum.
It is also introducing curfews with GPS tracking for families released in the US before initial asylum screenings.
As the deadline approaches record numbers of people have moved towards the border hoping to be allowed in.
Even President Joe Biden has acknowledged that the situation could be "chaotic". The federal government has mobilised more than 24,000 agents and police at the border.
"We are seeing a lot more females with children," explained human rights advocate Adriana Jasso. "If you take a look, we're looking at really small [children], like babies, from 2 to 3 years old, 5, 6, maybe 10 years old."
From Friday, would-be migrants must register their name, date of birth, and details of their travel documents, and upload a photograph on an app called CBP One. The app can also log their location and their device details.
But old, outdated phones make the process hard. It's harder still for those whose phones were broken or stolen on the long trek north.
Antonio Sanchez Ventura lives on the streets of Ciudad Juarez with nothing, eating only what he can scrounge. His sole focus now is to raise the money to buy a phone and download the app.
"It is the dream of every human being to cross to the United States to help our relatives," he said.
The Border Patrol stopped about 10,000 migrants on Tuesday, one of its busiest days ever, according to a US official who spoke on condition of anonymity because he was not authorised to speak publicly.
That's nearly double the daily average of about 5,200 in March, the latest publicly available data, and close to the 11,000 that US officials have predicted is the upper limit of a surge they anticipate after Title 42.
More than 27,000 people were in US Customs and Border Protection custody, the official said, well above capacity.
In March, 8,600 people were in custody.
Border Patrol agents were ordered to begin releasing migrants in any border sector that reached 125% of its holding capacity with instructions to report to an immigration office within 60 days, the official said.
They were also told to start the releases if the average time in custody exceeded 60 hours or if 7,000 migrants were taken into custody across the entire border in any one day.
New policies aimed at bringing order to migration
The US government says its new policies will offer pathways to legitimate asylum seekers, and harsh penalties to those who do not follow the rules.
Up to 30,000 people a month from Haiti, Cuba, Nicaragua and Venezuela can enter if they apply online with a financial sponsor and enter through an airport.
Processing centres are opening in Guatemala, Colombia and elsewhere. Up to 1,000 can enter daily through land crossings with Mexico if they manage to snag an appointment on the online app.
For Raul Pinto, an attorney with the American Immigration Council, the app's many problems add another layer of unnecessary despair.
"It's frustrating that this important process is left at the mercy of technology that can often be glitchy and that is not going to be accessible by everyone," he told the news agency AFP.
The government said this week it would be rolling out updates to the app and increasing the number of appointments available in a bid to ease the logjam.