US Attorney George E.B. Holding declined to discuss the whereabouts of the person at large but said the public should not be worried.
"Federal authorities hope to have him apprehended shortly," Holding said without elaborating. Holding wouldn't identify the person, and the defendant's name is redacted from court papers.
On Monday, US federal authorities said a father, his two sons and four other men living in North Carolina are accused of military-style training at home and plotting "violent jihad" abroad, including against targets in Israel.
Officials said the men were led by Daniel Patrick Boyd, 39, who resided in a small lakeside home in a rural area south of Raleigh, where he and his family walked their dog and operated a drywall business.
"These charges hammer home the point that terrorists and their supporters are not confined to the remote regions of some far away land but can grow and fester right here at home," US Attorney George E.B. Holding said.
The seven men made their first court appearances in Raleigh on Monday, charged with providing material support to terrorism. If convicted, they could face life in prison.
The indictment said Boyd, a US citizen, trained in Afghanistan and fought there between 1989 and 1992 before returning to the United States. Court documents charged that Boyd, also known as "Saifullah," encouraged others to engage in jihad.
Boyd's beliefs were so extreme that he stopped attending worship services in the Raleigh area this year and instead began holding meetings for Friday prayers in his home.
"This is not an indictment of the entire Muslim community," Holding said. "These people had broken away because their local mosque did not follow their vision of being a good Muslim."
In 1991, Boyd and his brother were convicted of bank robbery in Pakistan and were accused of carrying identification showing they belonged to the radical Afghan guerrilla group, Hezb-e-Islami, or Party of Islam. They were each sentenced to have a foot and a hand cut off for the robbery, but the sentenced was later overturned.
The wives of the men told The Associated Press in an interview at the time they were glad the truth about their husbands had finally become known. The wives said the couples had US roots but the United States was a country of "kafirs" - Arabic for heathens.
Jim Stephenson, a neighbor of Patrick Boyd in Willow Spring, said he saw the Boyd family walking their dog in the neighborhood. He said the indictment shocked the residents.
"We never saw anything to give any clues that something like that could be going on in their family," Stephenson said.
Two of the suspects are Boyd's sons: Zakariya Boyd, 20 and Dylan Boyd, 22. The others are Anes Subasic, 33; Mohammad Omar Aly Hassan, 22; and Ziyad Yaghi, 21.
Hysen Sherifi, 24, a native of Kosovo and a US legal permanent resident was also charged in the case. He was the only person arrested who was not a US citizen.
All were residents of North Carolina. No attorneys for the men were listed in court records.
Reached at her home in Silver Spring, Maryland, Boyd's mother said she had not heard of their arrests and knew nothing about the current case.
"It certainly sounds weird to me," Pat Saddler said. "That's news to me."
Hassan's father declined to comment Monday night while others did not have listed numbers or did not return calls.
It's unclear how authorities learned of the activities, although court documents indicate that prosecutors will introduce evidence gathered under the Foreign Intelligence Surveillance Act.
The indictment claims Boyd traveled to Israel in 2007 with several of the defendants, hoping to engage in "violent jihad." The attempt was unsuccessful, though, and the men returned home, officials said.
Boyd was also accused of trying to raise money last year to fund others' travel overseas to fight. One of the men, Hysen Sharifi, allegedly went to Kosovo to engage in violent jihad, according to the indictment, but it's unclear if he did any actual fighting.
Several of the defendants, including Boyd, were also charged with practicing military tactics on a private property in Caswell County in June and July of this year.