In muddy makeshift camps in the Mexican border city of Ciudad Juarez, more than 1,000 migrants had waited for weeks for a chance to request asylum in the United States, enduring cold nights and long days of uncertainty.

Frustrated, many are giving up and clearing out.

Authorities say as of last week, there were still about 1,400 migrants, most of them from southwestern Mexico, holding out hope under tents and tarps not far from the Rio Grande.

But on Thursday, only about 700 remained. The others grew tired of the near-freezing temperatures at night and the seemingly fruitless quest to be heard by U.S. officials.

Local associations convinced several families to head to shelters or hotels when the temperature started to plummet.

Some instead made their way across the river, without any idea if they would succeed.

And still others opted to remain – they are afraid to lose their place on the murky wait list system they themselves created to convince U.S. border agents to take them in order of their arrival.

"They won't let us proceed unless we hand them our slips to show them we have indeed been waiting," said Rosa, who keeps up the list on a daily basis.

Every night, the men and women at the camp keep watch on the comings and goings on the bridge crossing the Rio Grande – the natural, international border – to make sure new arrivals don't jump the queue.

(With input from AFP)