By Mariana Atencio and Nicole Acevedo

PIEDRAS NEGRAS, Mexico — Tensions flared as roughly 1,800 Central American migrants lost patience as they waited in an improvised shelter in Mexico for a chance to apply for refuge in the United States.

On Wednesday, some two dozen people broke through security barriers and rioted inside the abandoned factory complex where the Piedras Negras shelter is located, just across from Eagle Pass, Texas. Some threw pipes, tables, chairs and parts of a tent toward the Mexican officers.

Mexican authorities and riot police have been present since Tuesday night after a smaller riot broke out at the facility.

Migrants are complaining of harsh conditions at the shelter where they have been for more than a week.

Federal and state officials are not allowing the migrants to leave the shelter unless they have a Mexican humanitarian visa, and those allowed out temporarily were taken in vans under police escort in groups of about a dozen to a nearby store to buy supplies, or to the U.S. border to file asylum claims.

Although migrants receive food, medical care and help to process humanitarian visas, two mothers told NBC News through the shelter’s fence that they feel like they’re in a prison — saying they never thought that Mexico would treat them poorly.

A glimpse of the conditions inside the shelter surfaced overnight after Raíces, the largest immigration legal services nonprofit in Texas, shared audio of a migrant describing his life at the shelter.

“We’re looking for organizations that could send us hats, gloves, blankets, because it’s very cold in here,” the man said.

In the audio, the migrant calls for aid groups to have access to the shelter and for the U.S. government to drop their so-called ‘remain in Mexico’ policy. The Trump administration no longer allows migrants to request asylum at the border and stay in the U.S. to pursue their claim. Instead, the administration made an agreement with Mexico to keep asylum seekers south of the border.

So far, close to 2,000 law enforcement authorities, including the U.S. Customs and Border Protection and federal Mexican officers, have been sent to the area.

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