Four New York City correction officers were indicted in the Bronx on charges they beat up a Rikers Island inmate and then covered up the assault by forging paperwork.

Officers Michael Dorsainvil, Christopher Huggins, Mark Anglin and Ronald Donnelley pleaded not guilty at their arraignment in criminal court in the Bronx after a grand jury returned a 19-count indictment charging them in inmate Carl Williams' beating.

Williams was being escorted back to the George Motchan Detention Center on Rikers last March when he cursed at the officers for taking and throwing away a bag of food he was carrying, prosecutors said.

Surveillance video of the encounter shows Williams going back into a holding pen as Dorsainvil, Huggins and Anglin follow him in, eventually hitting him and forcing him to the ground, authorities said. The officers then filed reports saying Williams sustained his injuries after they used force to stop him from hanging himself, prosecutors said. Donnelley filed a witness report corroborating their account, they said.

"Correction officers who use force when it is unjustified and falsify the facts to cover it up undermine the safety and integrity of our city's jails and make the job of all correction officers more difficult," said Mark G. Peters, the commissioner of the Department of Investigation, which investigated the case along with the Department of Correction.

Dorsainvil, Huggins and Anglin were charged with gang assault, assault, offering a false instrument for filing and other crimes. Donnelley was charged with falsifying business records and other crimes. Their lawyers didn't immediately return calls for comment Friday.

The Department of Correction immediately investigated the case and referred it to the Department of Investigation for review, said a DOC spokesman, who added he couldn't comment directly on it.

The indictments came a day after The Associated Press reported exclusively based on an internal city report that nearly a third of Rikers Island inmates who said their visible injuries came at the hands of a correction officer last year suffered blows to the head, a tactic that's supposed to be used by correction officers as a last resort because it's potentially fatal.

The report, conducted by city health officials and obtained via a Freedom of Information request, also found that an average of three inmates a day were treated for visible physical injuries they claimed were caused by correction officers and 20 others were treated daily for injuries primarily resulting from inmate-on-inmate violence.

A spokesman for Mayor Bill de Blasio, who took office Jan. 1 and hasn't named a new DOC commissioner, didn't immediately respond to a request for comment Friday.