Federal prosecutors sued New York City on Thursday over alleged civil rights violations after a Department of Justice investigation found a "deep-seated culture of violence" against young inmates at the Rikers Island jail.

New York City Mayor Bill de Blasio, left, and Department of Correction Commissioner Joseph Ponte participate in a news conference on Rikers Island in New York, Wednesday, Dec. 17, 2014. Seth Wenig/AP

The DOJ's lengthy investigation found that the New York Department of Corrections "relies too heavily on punitive segregation as a disciplinary measure, placing adolescent inmates in what amounts to solitary confinement at an alarming rate and for excessive periods of time."

A 2012 photo shows Rikers Island inmate Robert Hinton in a medical clinic in New York, bloodied with a swollen face, shortly after a beating. Uncredited/AP

An administrative law judge recommended in September that the six officers involved in Hinton's brutal beating were fired, but this sort of excessive force persists at Rikers.

Editors Note: Mar. 2, 2015

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