A flare-up of inmate violence at Nassau County’s jail sent nine correction officers to the hospital Sunday night, prompting Sheriff Michael Sposato to institute a facility-wide lockdown until Tuesday morning, according to authorities.

The officers suffered mostly bumps and bruises in the jail dorm incident and hospital officials treated and released them, correction union leader Brian Sullivan said Tuesday.

A state Commission of Correction spokeswoman said the oversight agency is reviewing the incident “to determine if further investigation will occur.”

The melee broke out about 8 p.m. Sunday when one male inmate became unruly and started threatening officers and other inmates joined in and refused to go into their cells and be locked in, Sullivan said.

The union official said one inmate swung on an officer and other inmates began fighting each other before officers used pepper spray to try to control the violence.

Sposato said he hadn’t read reports on Sunday’s incident yet but had been told officers had to use force on two inmates and he’d received no indication inmates also had been fighting each other.

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Sullivan said a reduction in jail security posts made it more difficult for backup to arrive to help break up the violence — a claim Sposato later said wasn’t true.

“I haven’t cut any security posts. There’s just no truth to that,” the sheriff said. “We support the correction officers. This is a jail. There are fights.”

But Sullivan, a month after leading a labor rally at the jail, said correction officials “are being used as pin cushions by the inmates.”

In August, union members sounded a vote of “no confidence” in the sheriff and protested what they called jail security lapses.

Nassau County Correctional Center in East Meadow on Aug. 10, 2016. Photo Credit: FlyingDogPhotos.com / Kevin P. Coughlin

But Sposato fired back Tuesday, saying of Sunday’s incident: “There’s just no truth” that a “lack of policies and posts create these things.”

Sposato had said after August’s demonstration that employees were protesting because “they want to do less work than I want them to do,” after he changed 30-minute patrols in inmate housing areas to 15-minute patrols.