Hundreds of investigations are underway in all 50 states and many involve suspected IS supporters, law enforcement officials told ABC News.
The latest arrest came Saturday in New York, where the FBI had spent months surveilling a college student accused of being a "fervent supporter" of IS.
Munther Omar Saleh thought al Qaeda was getting soft, and the 20 year old from Queens was "making efforts to prepare an explosive device for detonation in New York," according to the FBI.
Court records quoted a 2014 tweet by Saleh that read: "I fear AQ could be getting too moderate." Saleh also allegedly offered to translate the terror group's propaganda into English, ABC reported.
Court documents say Saleh had carried out several online searches about building and detonating various explosive devices, including pressure cooker bombs like those used in the Boston Marathon bombing.
Saleh had been enrolled in an aeronautics program at Queens College since January and investigators believe that his knowledge of electrical circuitry would have helped him to construct a pressure cooker bomb or other explosive device, Fox News reported.
Investigators also found on Saleh's computer images of New York City landmarks and tourist attractions, which the FBI said were "potential targets for a terrorist attack."
A Port Authority police officer saw him walking with a lantern on the George Washington Bridge, according to court records. The FBI said Saleh told a confidential informant he was "in NY and trying to do an" operation.
Days later, FBI agents arrested 21-year-old Fareed Mumuni at a Staten Island home. A friend of Saleh, Mumuni was also under FBI surveillance. Authorities say he lunged at FBI agents with a knife as they searched the home.
In court papers, prosecutors allege that Mumuni "espouses violent jihadist beliefs and is a fervent supporter of (IS)" and that he, "made efforts to participate in or support a terrorist attack in the New York metropolitan area or elsewhere on behalf of (IS)."
