DEL RIO, TEXAS -- Haitian migrants seeking to escape poverty, hunger and a feeling of hopelessness in their home country said they will not be deterred by U.S. plans to speedily send them back, as thousands of people remained encamped on the Texas border Saturday after crossing from Mexico.

Scores of people waded back and forth across the Rio Grande on Saturday afternoon, re-entering Mexico to purchase water, food and diapers in Ciudad Acuna before returning to the Texas encampment under and near a bridge in the border city of Del Rio.

Junior Jean, a 32-year-old man from Haiti, watched as people cautiously carried cases of water or bags of food through the knee-high river water. Jean said he lived on the streets in Chile the past four years, resigned to searching for food in garbage cans.

"We are all looking for a better life," he said.

The Department of Homeland Security said Saturday that it moved about 2,000 of the migrants from the camp to other locations Friday for processing and possible removal from the U.S. Its statement also said it would have 400 agents and officers in the area by Monday morning and would send more if necessary.

The announcement marked a swift response to the sudden arrival of Haitians in Del Rio, a Texas city of about 35,000 people roughly 145 miles (230 kilometres) west of San Antonio. It sits on a relatively remote stretch of border that lacks capacity to hold and process such large numbers of people.

A U.S. official told The Associated Press on Friday that the U.S would likely fly the migrants out of the country on five to eight flights a day, starting Sunday, while another official expected no more than two a day and said everyone would be tested for COVID-19. The first official said operational capacity and Haiti's willingness to accept flights would determine how many flights there would be. Both officials were not authorized to discuss the matter publicly and spoke on the condition of anonymity.

Told of the U.S. plans Saturday, several migrants said they still intended to remain in the encampment and seek asylum. Some spoke of the most recent devastating earthquake in Haiti and the assassination of President Jovenel Moise, saying they were afraid to return to a country that seems more unstable than when they left.

"In Haiti, there is no security," said Fabricio Jean, a 38-year-old Haitian who arrived with his wife and two daughters. "The country is in a political crisis."

Haitians have been migrating to the U.S. in large numbers from South America for several years, many having left their Caribbean nation after a devastating 2010 earthquake. After jobs dried up from the 2016 Summer Olympics in Rio de Janeiro, many made the dangerous trek by foot, bus and car to the U.S. border, including through the infamous Darien Gap, a Panamanian jungle.

Jorge Luis Mora Castillo, a 48-year-old from Cuba, said he arrived Saturday in Acuna and also planned to cross into the U.S. Castillo said his family paid smugglers US$12,000 to take him, his wife and their son out of Paraguay, a South American nation where they had lived for four years.

Told of the U.S. message discouraging migrants, Castillo said he wouldn't change his mind.

"Because to go back to Cuba is to die," he said.

U.S. Customs and Border Protection closed off vehicle and pedestrian traffic in both directions Friday at the only border crossing between Del Rio and Ciudad Acuna "to respond to urgent safety and security needs" and it remained closed Saturday. Travelers were being directed indefinitely to a crossing in Eagle Pass, roughly 55 miles (90 kilometres) away.

Crowd estimates varied, but Del Rio Mayor Bruno Lozano said Saturday evening there were 14,534 immigrants at the camp under the bridge. Migrants pitched tents and built makeshif t shelters from giant reeds known as carrizo cane. Many bathed and washed clothing in the river.

It is unclear how such a large number amassed so quickly, though many Haitians have been assembling in camps on the Mexican side of the border to wait while deciding whether to attempt entry into the U.S.

The number of Haitian arrivals began to reach unsustainable levels for the Border Patrol in Del Rio about 2 1/2 weeks ago, prompting the agency's acting sector chief, Robert Garcia, to ask headquarters for help, according to a U.S. official who was not authorized to discuss the matter publicly.

Since then, the agency has transferred Haitians in buses and vans to other Border Patrol facilities in Texas, specifically El Paso, Laredo and Rio Grande Valley. They are mostly processed outside of the pandemic-related authority, meaning they can claim asylum and remain in the U.S. while their claims are considered. U.S. Immigration and Customs Enforcement makes custody decision but families can generally not be held more than 20 days under court order.

Homeland Security's plan announced Saturday signals a shift to use of pandemic-related authority for immediate expulsion to Haiti without an opportunity to claim asylum, the official said.

The flight plan, while potentially massive in scale, hinges on how Haitians respond. They might have to decide whether to stay put at the risk of being sent back to an impoverished homeland wracked by poverty and political instability or return to Mexico. Unaccompanied children are exempt from fast-track expulsions.

DHS said, "our borders are not open, and people should not make the dangerous journey."

"Individuals and families are subject to border restrictions, including expulsion," the agency wrote. "Irregular migration poses a significant threat to the health and welfare of border communities and to the lives of migrants themselves, and should not be attempted."

U.S. authorities are being severely tested after Democratic U.S. President Joe Biden quickly dismantled Trump administration policies that Biden considered cruel or inhumane, most notably one requiring asylum-seekers to remain in Mexico while waiting for U.S. immigration court hearings.

A pandemic-related order to immediately expel migrants without giving them the opportunity to seek asylum that was introduced in March 2020 remains in effect, but unaccompanied children and many families have been exempt. During his first month in office, Biden chose to exempt children traveling alone on humanitarian grounds.

Nicole Phillips, legal director for advocacy group Haitian Bridge Alliance, said Saturday that the U.S. government should process migrants and allow them to apply for asylum, not rush to expel them.

"It really is a humanitarian crisis," Phillips said. "There needs to be a lot of help there now."

Mexico's immigration agency said in a statement Saturday that Mexico has opened a "permanent dialogue" with Haitian government representatives "to address the situation of irregular migratory flows during their entry and transit through Mexico, as well as their assisted return."

The agency didn't specify if it was referring to the Haitians in Ciudad Acuna or to the thousands of others in Tapachula, at the Guatemalan border, and the agency didn't immediately reply to a request for further details.

In August, U.S. authorities stopped migrants nearly 209,000 times at the border, which was close to a 20-year high even though many of the stops involved repeat crossers because there are no legal consequences for being expelled under the pandemic authority.

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Lozano reported from Ciudad Acuna, Mexico and Spagat reported from San Diego. Associated Press writers Ben Fox, Alexandra Jaffe and Colleen Long in Washington contributed to this report.