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A New Jersey man who worked at the Philadelphia Navy Yard was sentenced to six months in prison for lying about his involvement in a white supremacist group, federal prosecutors in Pennsylvania said Thursday.

Fred Arena, 41, of Salem, New Jersey, was an employee of a federal contractor and falsely stated on a security clearance form in January that he was never a member of a group that used or advocated violence to prevent others from exercising their constitutional rights, the U.S. Attorney’s Office for the Eastern District of Pennsylvania said in a statement.

Arena was an "avowed member" of Vanguard America, a white supremacist group, prosecutors said.

U.S. Attorney William M. McSwain said in a statement that lying on the form, a Form SF-86, and to government agents was a serious matter.

"Further, no employee working for the federal government, being paid with taxpayer dollars, has any business being a member of a white supremacist group or espousing white supremacist views," McSwain said.

Arena was sentenced to six months in prison and two years of supervised release. He is also barred from being a member of a group that espouses violence.

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Federal prosecutors said in Thursday's statement that Arena's association with the group was "demonstrated by his many admissions and photos on social media."

Arena admitted his involvement with a white supremacist group and to lying about it but denied he was involved in any violent behavior, according to a sentencing memorandum filed by his attorney.

"Mr. Arena has since disavowed all relations with any white supremacist groups," the document states.

Emailed requests for comment from attorneys listed as representing him were not immediately returned Thursday night.

The Southern Poverty Law Center describes Vanguard America as a neo-Nazi group.

Prosecutors said in court documents that Arena posted photos of himself wearing Vanguard America apparel and participating in events surrounding the 2017 "Unite the Right" event in Charlottesville, Virginia.

Another man, James Alex Fields Jr., drove his car into counter-protesters, killing Heather Heyer, and was photographed at the event holding a shield with the Vanguard America emblem before the attack. The group later denied Fields was associated with them.

Fields has been sentenced to life in prison on federal counts, and was sentenced to a second life term plus 419 years on state counts.

Arena was arrested in October, and in December, he pleaded guilty to making false statements to government agents.

He was an environmental engineer who worked at the Navy yard for about two years before the criminal case, the sentencing memorandum says.

Arena was sentenced to six months in prison, but he has been in federal custody since Oct. 25 and a six-month sentence could mean he would be released around April 25, the sentencing memorandum filed before sentencing says.