The discovery of 50 bodies in a lorry near San Antonio in Texas on Monday is believed to be linked to people smuggling across the Mexican border.
If confirmed, it would represent the most deadly event of its kind in US history.
It also comes at a time of a surge in the number of people seeking to cross into the US, leading to Republican opponents of president Joe Biden arguing that he has lost control on the southern border.
Biden entered office promising to deal with immigration problems. However, the number of people making the dangerous journey from Central America to the Texan border has increased over the last year or so.
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Economic problems in countries such as Honduras, Guatemala, El Salvador, Nicaragua and Cuba, which got worse during the pandemic, as well as increasing gang violence are seen as factors behind the rising number of migrants.
There has also been a growing number of people from countries outside of the Americas such as India, Turkey and Russia seeking to cross the Texan border.
Earlier this month, US secretary of state Antony Blinken said the immigration challenges that the Biden administration was facing on its southern border are “beyond anything that anyone has seen before”.
Official figures show that the level of immigration-related arrests reached record levels in May.
The US custom and border patrol arrested 239,416 people in May, a rise of 2 per cent on the figure for April.
It is now expected that this year will see the total number of border arrests exceed the 1.73 million recorded in 2021.
Republican Texas governor Greg Abbott has accused the Biden administration of operating an effective “open border” regime.
In a report this month Republican senators argued that Biden administration policies had “incentivised illegal migration, eroded the security of our borders, and undermined US efforts to build effective law enforcement and asylum processing mechanisms across Mexico and northern Central America”.
“Lax enforcement of US immigration policies here at home weakens the incentives among governments to address challenges posed by illegal migration in their own countries. ”
Technically, the Mexican border is supposed to be sealed off under public health measures introduced during the pandemic by former president Donald Trump.
However, the operation of this arrangement and another Trump-era policy known as “remain in Mexico”, which requires migrants from a third country arriving through the southern border to wait outside the US while their asylum application is processed, has left Biden squeezed between his Republican opponents and liberals on his own side.
Progressives have criticised the administration for continuing with some of these policies inherited from Trump. However, Biden has reversed the Trump policy of separating families at the border which saw some parents deported without their children.
Since it was introduced in March 2020, the public health order known as title 42 has allowed border agents to quickly remove most migrants without giving them a chance to apply for asylum on the grounds that it was due to safety concerns as a result of the pandemic. Many are just sent back to Mexico.