Former Rep. Beto O'Rourke of Texas on Thursday excoriated President Donald Trump during a visit to a detention facility for migrant children in Florida.

"It is only when the president has given permission do you see kids put in cages or detained in tent cities like this one," O'Rourke said after INSIDER asked if he had a message for Trump.

O'Rourke visited the detention facility the morning after he participated in the first 2020 Democratic presidential debate in Miami.

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HOMESTEAD, FLORIDA — Former Rep. Beto O'Rourke on Thursday lambasted President Donald Trump on immigration as he visited a migrant child detention facility in Homestead, Florida.

It was a boiling hot day and O'Rourke struggled to hold back his emotions as he addressed local activists and reporters. Moments after O'Rourke joined activists in calling out to migrant children who could be seen walking outside in the facility, INSIDER asked the presidential hopeful if he had a message for Trump.

"This is what happens when you call Mexican immigrants 'rapists' and 'criminals.' This is what happens when you call asylum seekers 'animals' and an 'infestation.' It is only when the president has given permission do you see kids put in cages or detained in tent cities like this one," O'Rourke said.

"All of us need to stand up and reclaim this country, and what we mean to ourselves, to the rest of the world, and to these kids," O'Rourke went on to say. "Donald Trump has done this but it is up to us to change who's in the White House going forward. It's up to us — right now — to apply the pressure, to form the political will, to see if we can get them to change these practices even when he's in the White House... We are counting on one another — right now."

O'Rourke visited the detention facility the morning after he participated in the first 2020 Democratic presidential debate in Miami. The Texan wasn't the only 2020 candidate to go to Homestead, however, as he arrived moments after Sen. Bernie Sanders of Vermont left after a tour of the facility. The detention center, where approximately 2,300 migrant children are currently confined, is on federal property run by a private, for-profit company.

Responding to O'Rourke's message to the president, Andrew Clark, the rapid response director for Trump's 2020 campaign, in a tweet said, "O'Rourke again repeats the false claim that President Trump called immigrants 'animals.' He did not say this. Fact check FALSE."

Trump on May 16, 2018 said some unauthorized immigrants "aren't people" but "animals" who will be taken out of the country "at a rate that's never happened before." The president at the time was responding to a California official's remarks on MS-13 gang members.

O'Rourke has been especially critical of Trump on immigration, and earlier this week blamed the president for the deaths of a migrant father and his young daughter.

The detention center for migrant children in Homestead, Florida. John Haltiwanger/INSIDER

The father, Oscar Alberto Martínez, and his 23-month-old daughter, Angie Valeria, died while attempting to cross the Rio Grande to enter the US. Originally from El Salvador, a nation plagued by violence and poverty, they'd hoped to seek asylum in the US.

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An image of Martínez and his daughter — their dead bodies lying facedown in murky water on the banks of the Rio Grande — went viral on social media over the past several days, prompting reactions across the globe.

Critics of the president have portrayed the image as a grim reminder of his opposition to asylum seekers entering the US, and efforts to make the process more difficult.

"If you are horrified by the tragic images from the Rio Grande and the recent deaths of migrants in the desert, you are not alone," Amnesty International said on Wednesday. "These deaths are the result of Trump Admin policies that deny families their legal right to seek asylum and force them into desperate circumstances."

Filippo Grandi, the UN High Commissioner for Refugees, in a statement on Wednesday said, "The deaths of Oscar and Valeria represent a failure to address the violence and desperation pushing people to take journeys of danger for the prospect of a life in safety and dignity. This is compounded by the absence of safe pathways for people to seek protection, leaving people with no other choice than to risk their lives."

Meanwhile, Trump has blamed Democrats for the deaths.