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A former New Jersey resident was ordered held without bond Monday on charges of attempting to provide support to ISIS.

The U.S. Justice Department said the charges against Nader Saadeh, 20, were the result of an FBI investigation into a group of individuals from New York and New Jersey. Several others were arrested in June and have already been charged.

Saadeh lived in New Jersey until he left the U.S. in May to allegedly join ISIS, according to the Justice Department. It wasn't immediately clear how and when he returned to the U.S., but the Justice Department said he was arrested Monday morning in New Jersey.

Saadeh sent "electronic messages" expressing his hatred for the U.S. in 2012 and 2013 and posted images of the ISIS flag on Facebook in 2014, according to the Justice Department.

He later allegedly became a "radicalized supporter" of the terrorist group and expressed support for ISIS-related attacks in Paris.

Saadeh — identified as a former resident of Bergen County — was charged in U.S. District Court in Newark with conspiring with other individuals in New Jersey and New York to provide material support to ISIS and with attempting to provide material support to the terrorist organization.

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Nader Saadeh appearing in court Monday. Courtesy Christine Cornell

The investigation into Saadeh began when a friend contacted the FBI and expressed concerns that Saadeh, his brother and others were planning to travel overseas and possibly join a terrorist group.

The friend — identified by the Justice Department as "Individual 1" — chronicled how the suspect's "adoption of stringent religious behavior" had coincided with "numerous statements in support" of ISIS, according to the criminal complaint against Saadeh.

When Saadeh told "Individual 1" he was planning to go study theology overseas, "Individual 1" became "very suspicious because Saadeh had never been very studious," the complaint said.

Search warrants unearthed texts between Saadeh and his mother in which Saadeh's mother urges him to "not go anywhere if u love me."

The complaint said Saadeh — a dual U.S.-Jordanian national — boarded a flight May 5 from New York to Amman, Jordan. He apparently was detained upon arrival.

At some point between May 5 and Monday — the day Saadeh was charged — others involved in the alleged conspiracy were arrested and apparently implicated him.

Saadeh's brother, Alaa, was apparently one of them. Alaa Saadeh was arrested June 29 and indicted on similar charges of conspiring to provide support to ISIS.

According to the criminal complaint, Alaa Saadeh told the FBI that he and his brother had watched ISIS propaganda videos and discussed going overseas to join the group.

Alaa Saadeh also said his brother was given the name and number of an ISIS contact near the Turkish-Syrian border before he left for Jordan to "facilitate" travel to the group's territory, according to the complaint.

"Alaa admitted that at one point he had wanted to join ISIL himself, but no longer believed they 'were good,'" it added. ISIL is another name for ISIS.