By Nate Raymond

NEW YORK (Reuters) - Three former New York state jail guards were arrested on Wednesday on federal charges that they participated in the 2013 beating of an inmate who suffered life-threatening injuries and had a clump of dreadlocks ripped from his head as a "trophy."

Kathy Scott, George Santiago and Carson Morris, who were all correction officers at the Downstate Correctional Facility in Fishkill, New York, were charged in an indictment filed in federal court in White Plains.

Two other ex-officers, Donald Cosman and Andrew Lowery, have pleaded guilty in connection with the beating of Kevin Moore, who was hospitalized for 17 days. Both men are cooperating with authorities.

The charges were announced by U.S. Attorney Preet Bharara, whose office has pursued several cases involving violence against inmates at jails in the state, such as New York City's Rikers Island complex.

"Excessive use of force in prisons, we believe, has reached crisis proportions in New York state," Bharara said.

Scott and Santiago were arrested in New York, while Morris was arrested in Florida. At a court hearing, Scott and Santiago pleaded not guilty to charges that included conspiracy to deprive civil rights and conspiracy to falsify records.

Martin Geduldig, Scott's lawyer, said she "will vigorously contest the charges." Lawyers for Santiago and Morris did not respond to requests for comment.

Prosecutors said the Nov. 12, 2013, beating came after Moore, who was to be housed in the jail temporarily for one night, questioned why he needed to be confined in a unit for inmates with mental health issues.

Prosecutors said Santiago, Morris, Cosman and Lowery beat Moore with fists, boots and batons, while Scott, a sergeant, watched without doing anything to stop them.

Moore sustained five fractured ribs, a collapsed lung and facial fractures, as well as severe back, hand, leg and foot contusions, prosecutors said.

A clump of dreadlocks was ripped from his head, which one officer took as a "trophy," the prosecutors said.

After the beating, prosecutors said, the officers tried to cover it up, with Santiago, Morris and others agreeing to pretend the inmate had attacked an officer.

To stage the story, Santiago struck Cosman in the back with a baton to cause injury marks, which Scott photographed, according to prosecutors. The officers also agreed to write a false report, they said.

A lawsuit by Moore over the incident remains pending. His lawyer, Philip Hines, said Moore was "extremely pleased" by Wednesday's charges.

(Reporting by Nate Raymond in New York; Editing by James Dalgleish and Peter Cooney)