Freezing temperatures hit the city of Ciudad Juárez on Wednesday, putting at risk hundreds of migrants who have set up camp near bridges linking the Mexican city to the United States.
About 550 people waiting to apply for asylum in the US are staying in tents on the streets near the border crossing points, regional government officials say. Nearly half of them are children younger than 12.
Most of them are Mexican nationals fleeing poverty and high levels of crime.
With temperatures dropping below freezing this week and predicted to stay low throughout the weekend, Mexican officials tried to move those living on the streets into shelters such as El Buen Samaritano (The Good Samaritan).
But many of those camped outdoors said they did not want to leave for fear of missing their spot in the queue of those crossing the bridges to seek asylum.
The US Customs and Border Protection agency has introduced strict limits on the number of people it allows to file asylum claims at ports of entry every day under an informal policy called "metering".
This creates a backlog on the Mexican side of the border where the wait can be anything from days to months.
A waiting list kept by Mexican officials in Ciudad Juárez currently runs to 1,200 names. The officials say they are seeking a meeting with their US counterparts to create a system in which those next on the list can be located and taken to the border without the need to camp out by the border bridges.
The numbers of those in the camps has dropped since August from 3,500 to 550, with many of those leaving saying they feared exposing their children to the winter temperatures.
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