A Texas tent city constructed last week to shelter migrant children became a protest site Sunday as crowds marched to oppose the separation of immigrant families at the border.

More than 200 children are being housed in the makeshift tent structure built in Tornillo, Tex., according to Rep. Beto O’Rourke (D-Tex.), who organized Sunday’s protest.

Protesters braved the Texas heat, carrying signs featuring slogans like, “Don’t use children to get your wall,” “Fight ignorance, not immigrants,” and “This is how the Holocaust started,” the El Paso Times reported.

“We’re wanting to make sure that everyone in this country knows what is happening here, in their name, in Tornillo, where kids have traveled 2,000 miles, some alone, some with their parents, are being held in detention camps, tent cities that have just been constructed over the course of this last week,” O’Rourke said.

The Trump administration chose Tornillo last week as the site of its first temporary shelter for children crossing the border. It has the capacity to house 360 children but plans to expand.

Thousands came out to protest Trump Administration's policy of separating families. #Tornillo is where the first tent city has been set up, with the possibility of holding 4000 children. More on the #immigration debate on @CBSNews w/@Elaine_Quijano tonight. pic.twitter.com/FqvQZLc84a — Mireya CBS (@cbsmireya) June 17, 2018

The use of temporary shelters plays into the “zero tolerance” policy, unveiled last month, which aims to prosecute more people entering the country illegally ― even if that means separating children from their parents. Nearly 2,000 children were separated from their parents by U.S. authorities between April 19 and May 31, a Department of Homeland Security official said on Friday.

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Department of Homeland Security Secretary Kirstjen Nielsen, meanwhile, denied the existence of any family separation policy.

“This misreporting by members, press and advocacy groups must stop,” Nielsen tweeted Sunday. “It is irresponsible and unproductive. As I have said many times before, if you are seeking asylum for your family, there is no reason to break the law and illegally cross between ports of entry.”

A number of prominent Republicans came out against the separation of families in recent days. Former First Lady Laura Bush called it “cruel” and “immoral.” First Lady Melania Trump said she “hates to see children separated from their families and hopes both sides of the aisle can finally come together to achieve successful immigration reform.” House Speaker Paul Ryan (R-Wis.) also voiced his disagreement, suggesting Congress push legislation to limit family separation.

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May 1920s

U.S. border guards check entering Mexicans

May 1920s

U.S. border guard and Mexicans behind the border fence.

March 21, 1929

A line of cars carrying Mexicans over the border into California. The fence in the foreground is the border; the line of cars is in the main street of Mexicali.

1930s

A flock of sheep at the border between Mexico and the United States.

June 1937

A pic of state border plant inspection maintained by the United States Department of Agriculture between Mexico and the United States. Shoppers returning from Mexico (Juarez) to the United States (El Paso) over the bridge that carries all the traffic are required to open their packages for inspection.

June 1937

Crossing the international bridge between Juarez, Mexico and El Paso, Texas.

June 1937

Mexicans entering the United States via the United States immigration station at El Paso, Texas.

1943

U.S. soldiers exchanging money at the U.S.-Mexico border.

March 15, 1950

A view of the Sigma Pi sorority crossing under the Mexico border sign to Tijuana, Mexico in Calexico, California.

1950s

Pregnant woman at the border.

1954

Mexican farm laborers standing on the Mexican side of the border trying to get into the U.S.

1954

Mexican workers waiting just inside the U.S. border to be let in.

October 1, 1962

A border guard checks passes of Mexicans entering the United States near Nogales, Mexico.

1967

Mexican workers crossing the border into Texas have their papers checked.

Sept. 22 1984

Suspected undocumented immigrants cross into the U.S. from Tijuana, Mexico.

1990

Men look across to the other side of the Tijuana border.

1990

Woman walking along the America-Mexico border, near Tijuana.

1993

U.S. Customs agents patrolling the border.

1994

At first light, undocumented immigrants wait to cross over into the United States.

1994

Undocumented immigrants wait on the other side of Mexico.

Aug. 19, 1997

Esther Pereyra Rubalcaba (left) kisses her daughter Patricia through the wall separating the US and Min Tijuana, Mexico.

July 20, 2005

Migrant activists lean against the border fence to pay homage to undocumented immigrants who died crossing over.

Aug. 28, 2005

Young Mexican nationals peer through the border wall at the beach along San Ysidro, California.

June 6, 2015

Paper doves in the shape of a heart are seen at the border fence in Ciudad Juarez, Mexico.

Sept. 25, 2016

Maria Rodriguez Torres, 70, looks towards her departing grandchildren after seeing them for the first time at the U.S.-Mexico border fence in Tijuana, Mexico. She had traveled with family members from Mexico City to see her grandchildren through the fence at "Friendship Park."

Oct. 6, 2016

A burnt car is seen next to a section of the wall separating Mexico and the United States in Tijuana, Mexico.

Feb. 4, 2017

A visitor stands next to the U.S.-Mexico border fence at Friends of Friendship Park in San Ysidro, California.

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