NEW YORK (AP) — The newly appointed commissioner of New York City's jail system violated city law by sending as many as 47 mentally ill inmates into 23-hour confinement without first getting approval from mental health clinicians, a city oversight board said Tuesday.

Commissioner Joseph Ponte, who took the helm of the country's second-largest jail system in March, insisted at a meeting of the New York City Board of Correction he was trying to quell rising levels of violence.

Ponte, who had reduced the use of solitary confinement by two thirds in Maine's state prisons, said the June 13 move on Rikers Island was aimed at volatile inmates who have broken jailhouse rules and owe days in solitary.

But board members rejected the argument, noting the move jeopardized the health of some inmates, particularly those on psychotropic medications who were taken from air-conditioned mental observation units and put into uncooled solitary cells. A federal judge has ordered that such inmates, deemed heat-sensitive because the exposure to heat while on such drugs can be fatal, shouldn't be placed in uncooled cells.

Other inmates who were moved were denied medication and had seizure disorders, they said. At least one inmate suffered a seizure, Ponte said.

"I would just hope that you would review these issues and in the future instruct your staff to be consistent with the board standards and not to violate these rules which are not just rules but designed for the safety of the prisoners," said board member Dr. Robert Cohen.

Nearly 40 percent of the roughly 11,500 daily inmates in city jails have a mental health diagnosis, according to the Department of Correction and about a third of them suffer from serious mental illnesses such as schizophrenia and bipolar disorder. The Associated Press has previously disclosed the deaths of two mentally ill inmates — one who essentially baked to death in a 101-degree cell in February — that have prompted calls for reform.

During a City Council oversight hearing on violence and mental illness at Rikers the day before the inmate moves, Ponte was repeatedly asked about a list of hundreds of inmates who owe time in solitary confinement but are in general population because there's not enough space. Correction officials argue that those inmates, many of whom they say are gang members, drive the violence on Rikers.

On Tuesday, Ponte told board members that figure is closer to 1,000 inmates. A number of them are high-risk for harming themselves and others and needed to be separated to stem surging violence, he said.

"What we don't have, and have not had for probably more than five years now, is a plan that's impacted the level of violence on Rikers Island," he told the board.

There were 21 slashings in one recent six-week period and a total of 87 during fiscal year 2014, according to a letter sent by Ponte to board members Monday night and obtained by the AP. There were a total of 68 total such slashing the previous fiscal year and 55 in fiscal 2012, the letter said.

"Under such circumstances, I felt that it was imperative to take prompt action to prevent further violence," he wrote.