The UN's High Commissioner for Human rights has said she's "deeply shocked" by the conditions in migrant and refugee detention centres near the US border.
Michelle Bachelet also said that children should never be held in immigration detention or separated from their families.
She was speaking amid a series of reports revealing details of overcrowding in centres where people are held after crossing the US-Mexico border.
Last week, the US Department of Homeland Security's Inspector General released a report calling for action to address 'dangerous overcrowding' in facilities in the Rio Grande Valley.
Inspections at five facilities found that 8,000 detainees were in custody - including 3,400 who were being held longer than the 72 hours generally allowed.
US media outlets have also reported on conditions - including a New York Times feature over the weekend citing allegations such as 'outbreaks of scabies, shingles and chickenpox' at one centre in Texas.
A number of high-profile US politicians have also visited the centres to highlight conditions faced by adults and children:
These are concentration camps.
According to concentration camp experts, people begin to die due to overcrowding, neglect, and shortage of resources.
We saw all three of those signs on our trip yesterday. Another person died yesterday.
And those are the deaths we know about. https://t.co/MhujNAYohJ
— Alexandria Ocasio-Cortez (@AOC) July 2, 2019
In a statement released today, UN High Commissioner for Human Rights Michelle Bachelet asked people to consider the "damage being done every day" in the current "alarming situation" at the US border.
She observed: “As a paediatrician, but also as a mother and a former head of State, I am deeply shocked that children are forced to sleep on the floor in overcrowded facilities, without access to adequate healthcare or food, and with poor sanitation conditions."
Mrs Bachelet stressed that detaining children for even a short period of time in good conditions can have a 'serious impact' on their health.
The former Chilean president further suggested that depriving adult migrants and refugees of their liberty should be a "measure of last resort".
She added: “In most of these cases, the migrants and refugees have embarked on perilous journeys with their children in search of protection and dignity and away from violence and hunger.
"When they finally believe they have arrived in safety, they may find themselves separated from their loved ones and locked in undignified conditions. This should never happen anywhere.”
US President Donald Trump has previously said illegal immigrants unhappy with conditions in "quickly built or refitted detentions centers" shouldn't come to the US.
However, he also accused the New York Times of writing "phony and exaggerated accounts" of conditions: