(CNN) Mexico's foreign minister on Tuesday added his voice to the chorus condemning the Trump administration's separation of children from their parents at the southern US border, calling the policy "cruel and inhumane."

Foreign Minister Luis Videgaray referred to one case involving a 10-year-old girl with Down syndrome as "particularly painful." He said the girl and her brother were sent to a US facility in McAllen, Texas, while her mother went to one an hour away in Brownsville.

The Mexican consulate in McAllen is working to get the girl released so she can be united with her father, the foreign minster said. The father is a legal US resident.

Videgaray said the Mexican government was aware of 21 Mexican children who have been separated from parents. Seven are still in US detention.

"The Mexican government in no way promotes illegal migration," he said. "However, according to our constitutional principles and our convictions, we cannot be indifferent before an act that clearly represents a violation of human rights and that puts into a vulnerable position minors, children, including those with disabilities."

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