Street gang members are becoming increasingly violent behind bars at the Nassau County Jail, according to the head of the correction officers union.

Brian Sullivan, the union president, says there are about 250 gang members in the jail, including 30 to 40 identified MS-13 members.

"They're becoming more emboldened, more violent, more territorial," he says. "When you're in a confined space like that, there's obviously going to be tensions."

There has been a rash of fistfights and slashings behind bars. One inmate who is suspected of being an MS-13 member was arrested for a recent machete attack in Westbury. Following his incarceration, he was gashed in the face from his eye to his ear by another inmate.

Sullivan says there have been six inmate slashings so far this year, compared to 10 in all of last year. He says it underscores ongoing problems like weapons being smuggled into the jail, and the need for more staffing.

"We need to do some massive hiring here," he says. "We need to hire 100 to 150 corrections officers."

Sullivan says the smuggled weapons could be coming in on truck deliveries. But he says there's simply not enough officers to search every shipment.

He blames the Nassau sheriff for trying to stay "under budget" by closing some of the housing units in the jail and not paying overtime so that officers can search the entire facility.

Democratic Nassau Legislator Kevan Abrahams says the issues are concerning. "Obviously the budget needs to be increased so we have the proper security at the jail," Abrahams says. "We understand the jail could be a very violent community, but if we're not doing the proper checks to secure the area, shame on Nassau County and shame on the sheriff."

In a statement, the Nassau sheriff denied that there’s been an increase in inmate violence. He says officers continually monitor the behaviors and activities of the inmates, and conduct searches on both a random and targeted basis. All correction officers were also recently fitted for stab-resistant vests to help protect them.