An investigation shows violence at Rikers Island, New York City's main jail, remains high, despite recent scrutiny on brutality at the jail. Above, inmates of Rikers Island Correctional Facility hug each other during a service held the day before Christmas in New York Dec. 24, 2013. Reuters/Lucas Jackson

Violence against inmates at Rikers Island in New York City is undiminished despite an investigation in recent months of violence and brutality at the prison, the New York Times reported Sunday. Instances of violence in 2014 were at their highest in a more than decade, yet the number of prisoners actually had decreased in the same period, the investigation showed.

After reviewing hundreds of pages of reports from the New York City Department of Correction, the Times reported, "Taken together, they suggest that in the face of an unprecedented push to reform Rikers, guards are either being defiant or are indifferent to demands for change."

The data from the department showed guards at Rikers used physical force against inmates more than 4,000 times in 2014. That number was the highest in more than a decade, even though the jail's prisoner population has fallen from 14,000 inmates a decade ago to 10,000 this year.

The Times identified and examined 62 beatings where corrections officers seriously harmed inmates, including those who suffered severe mental illness. It found 70 percent of the beatings resulted in head injuries and more than half led to broken bones among inmates. The brutality leading to the injuries existed despite a policy that calls for guards to avoid hitting prisoners in the head except when necessary, the Times said.

The inmates at Rikers weren't the only ones sustaining injuries, however. Nearly half the guards in 30 incidents that took place from August to January broke bones in their hands, something that can happen with punches to the head.

A statement from the department said change in Rikers' culture would take time. "We are, however, on our way to a jail system that is safer and more humane," it said.

"Changing the culture of violence on Rikers Island will not be easy or quick," Dr. Robert Cohen, a member of the Board of Correction, a city watchdog agency, told the Times. "The demonization of detainees is embedded in everyday practice."

The Times' discoveries come after a period of months in which attention was heaped on the prison for its violent culture against inmates, and government officials promised reform. In July 2014, the Times had published an investigation into violence against and injuries among inmates at Rikers in 2013. In August 2014, the U.S. attorney's office in Manhattan issued a report of its own based on a 2 1/2-year investigation into the treatment of adolescent inmates that found a "deep-seated culture of violence" for Rikers' teenage inmates.

New York City Mayor Bill de Blasio announced in November that ending violence at Rikers was a priority. But in December, U.S. Attorney Preet Bharara decided to sue the city for civil rights violations of adolescent inmates at Rikers, a case that remains unsettled.