Solitary confinement may no longer be used to punish teenagers jailed on Rikers Island in New York City, but the move, announced Wednesday by New York City Mayor Bill de Blasio, wasn’t enough to stop a federal lawsuit against the city on Thursday. The U.S. attorney for Manhattan said the city was too slow in adopting reforms of the jail in wake of a scathing report that found corrections officers use violence against inmates “not as a last resort, but as a means to control the adolescent population.”

Negotiations between the city and federal prosecutors were ongoing for months before U.S. Attorney Preet Bharara filed the lawsuit Thursday in Manhattan federal court.  “While the United States had hoped to reach a speedy resolution with the city on these critical issues, thus far insufficient progress has been made,” he wrote, according to the New York Times.

A 986-page report filed in August by the U.S. attorney’s office found that force was used against adolescent inmates at Rikers “at an alarming rate” and that “violent inmate-on-inmate fights and assault are commonplace, resulting in a striking number of serious injuries.” The office also found that corrections officers punch adolescent inmates in the face “too frequently,” and that they would justify their attacks on the inmates by yelling “stop resisting,” even if the inmates weren’t resisting or had already been subdued.

Administrative problems were also uncovered on Rikers Island, including false and inadequate reporting of use of force by staff and insufficient investigations into the violence. Inmates were found to be poorly supervised and there were “general failures by management to adequately address the extraordinarily high levels of violence perpetrated against and among the adolescent population.”

The youth, including those who were mentally ill, were also subject to “punitive segregation,” which the U.S. attorney’s office described as a tactic that “amounts to solitary confinement.”  The feds said the method of punishment “can cause significant psychological, physical and developmental harm to adolescents,” including paranoia, anxiety and depression just from a short period in solitary confinement.

De Blasio said Wednesday that solitary confinement ended under his administration on Dec. 4. “By ending the use of punitive segregation for adolescents, we are shifting away from a jail system that punishes its youngest inmates, to one that is focused on rehabilitation with the goal of helping put these young New Yorkers on the path to better outcomes,” he said in a statement. “[Corrections] Commissioner [Joe] Ponte is a proven change agent and [Wednesday’s] announcement is one of a series of reforms under his leadership that will begin to stabilize the situation and unwind the decades of neglect that have led to unacceptable levels of violence on Rikers Island.”

But Bharara still pressed on with a lawsuit aimed at ensuring that 73 recommendations from his office are followed by the city, the Associated Press reported. "To date, defendants have failed to take sufficient and effective measures to remedy these deficiencies," the lawsuit states.

The suit was filed a day before Bharara successfully prosecuted a former Rikers Island captain who was found to have ignored a dying inmate’s pleas for help, New York 1 reported. Terrence Pendergrass, 50, was convicted of deprivation of rights against 25-year-old Jason Echevarria, who suffered from bipolar disorder and swallowed a ball of soap filled with detergent, according to the station.

Earlier this month, a Rikers Island correction officer, 34-year-old Carol Lackner, was charged with lying on jail records in the death of 56-year-old Jerome Murtaugh, the Times reported. Murtaugh, who was mentally ill, was found to have likely died of dehydration or heat stroke and "basically baked to death," according to the AP. Lackner pleaded not guilty. She is accused of falsifying records by saying that she checked on inmates six times when she was on duty the day Murtaugh when surveillance video did not corroborate her reports, the Times reported. 

In August, the AP exposed the deaths of three inmates within a five-year period that appeared to be caused by guards who beat them. None of the guards faced charges, even though the deaths were rules as homicides.