WASHINGTON (AP) — This story is part of an ongoing joint investigation between The Associated Press and the PBS series FRONTLINE on the treatment of migrant children, which includes an upcoming film.

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Dozens of families separated at the border as part of the Trump administration's zero tolerance policy are preparing to sue the federal government, including several who say their young children were sexually, physically or emotionally abused in federally funded foster care.

A review of 38 legal claims obtained by The Associated Press — some of which have never been made public — shows taxpaye...