Alaa Saadeh, 23, of West New York, New Jersey, was expected to appear in Newark federal court later on Monday, the U.S. Justice Department said.

According to a criminal complaint, Saadeh was working with Munther Omar Saleh, a college student from Queens who was arrested on June 13 along with an unnamed co-conspirator when the two men charged a surveillance vehicle. 

Authorities have accused Saleh of planning to set off an explosive device in New York on behalf of Islamic State.

Saadeh also communicated frequently with Samuel Topaz, another New Jersey man arrested in connection with the alleged conspiracy on June 17, the complaint said.

The same day, authorities arrested Fareed Mumuni, 21, at his home in New York when he attacked an FBI agent with a knife during the execution of a search warrant connected with the case.

Saadeh’s brother, whom authorities have not named but have said was also a member of the group, traveled overseas in May in order to join Islamic State, according to the Justice Department.

U.S. authorities said on Monday that he had been arrested in Jordan for allegedly supporting Islamic State.

Saadeh is accused of helping his brother make travel arrangements and of planning with Topaz and Saleh to reunite with his brother overseas at some point to help Islamic State.

In April, an unnamed individual who lived with Saadeh and his brother in New Jersey contacted the FBI and said he believed they and others were planning to travel abroad to join a militant group.

Saadeh would later tell the individual to lie to the FBI, according to the criminal complaint. He is charged with witness tampering in addition to two terrorism counts.

In recent months, U.S. authorities have charged numerous individuals with providing support for Islamic State or conspiring to do so.