(CNN) A Guatemalan mother whose toddler died weeks after being released from a Texas immigrant family detention center is suing the private prison company that operates the facility.

Yazmin Juárez, who testified in Congress earlier this month about her 21-month-old daughter's death , filed a lawsuit Wednesday seeking $40 million in damages from CoreCivic, which runs the South Texas Family Residential Center in Dilley, Texas.

Juarez and her daughter, Mariee, were detained for three weeks at the 2,400-bed facility last year. Mariee died six-and-a-half weeks after their release.

"CoreCivic held families and small children in overcrowded quarters, creating prime conditions for the spread of sickness, and did nothing to ensure that those families and children received adequate medical care," the lawsuit says. "As a result of CoreCivic's recklessness, negligence, and callous indifference to the health and safety of the families and small children detained at Dilley, Mariee suffered an agonizing death, and Ms. Juárez suffered the unimaginable pain of watching her only child sicken, suffer, and die before her eyes."

A spokeswoman for CoreCivic said medical and mental healthcare services at Dilley are the responsibility of the ICE Health Service Corps, and referred questions about medical and mental health treatment there to Immigration and Customs Enforcement. The agency did not immediately respond to CNN's request for comment.

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