NEW YORK (AP) — Inmates at New York City’s Rikers Island were kept locked in their cells for nearly half an hour while a fire spread through one of the nation’s largest and most notorious jail complexes this past April, injuring some 20 people, according to a report released Friday by an independent oversight agency.

The city Board of Correction also found that the water supply for the sprinkler system serving the affected jail unit had been shut off for at least a year and that jail staff had failed to conduct the required weekly and monthly fire safety audits for at least as long.

In addition, the correction officer assigned to the area, at the direction of their supervisor, stopped conducting patrols some two hours before the fire was ignited in a unit that houses people with acute medical conditions requiring infirmary care or Americans with Disabilities Act-compliant housing, the board found.

Spokespersons for Mayor Eric Adams didn’t reply to an email seeking comment Friday, but his administration’s Department of Correction, which operates city jails, said it will review the report and its recommendations.

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The Legal Aid Society, an advocacy group that’s been critical of operations at Rikers, said the report highlighted “egregious mismanagement” and called into question the correction department’s ability to effectively run the jail complex, which faces a possible federal takeover as well as a long-gestating city plan to close the complex outright.

“The Report describes layers upon layers of avoidable failures,” the organization wrote in an emailed statement. “It is hard to imagine any institution in our city where such compounding and colossal failures to prevent and contain a catastrophic fire would not result in immediate accountability by leadership.”

The April 6 fire injured 15 jail staffers and five inmates and took about an hour to knock down on a day when local Democratic lawmakers were also touring the facility.

The afternoon blaze was set by a 30-year-old inmate with a history for starting jailhouse fires, according to the board’s report. The man used batteries, headphone wires and a remote control to start the conflagration in his cell, before adding tissues and clothing to fuel the flames.

The board, in its Friday report, recommended corrections officers immediately open cell doors and escort inmates to safety if they’re locked in a cell when a fire starts. It also recommended the department conduct regular sprinkler system checks and stop the practice of shutting off a cell’s sprinkler water supply because an inmate has flooded their cell.

Earlier this week, the New York City Council approved legislation meant to ban solitary confinement at Rikers and other city jails, over the mayor’s objections.