(CNN) A 10-year-old Mexican girl with Down syndrome is among the thousands of children who have recently been separated from their parents at the southern US border, Mexico's foreign minister said.

The girl and her brother were sent to a detention center in McAllen,Texas, and their mother was sent to a facility about an hour away in Brownsville after the family attempted to cross the border.

Foreign Minister Luis Videgaray said the Mexican consulate along with the girl's father, a legal US resident, are working to get the girl released.

It's a "particularly painful case," Videgaray said.

The US Customs and Border Protection issued a statement saying the mother is not being prosecuted under the zero tolerance policy.

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