The Islamic State has likely radicalized thousands of people in the United States, according to a new report, raising concerns that supporters of the terrorist group could be plotting domestic attacks similar to the recent shootings and bombings in Paris.

The Threat Knowledge Group, an organization led by the counterterrorism experts Sebastian and Katharine Gorka, has compiled a list of 82 individuals in the United States who were affiliated with the Islamic State (also known as ISIS or ISIL) and apprehended by law enforcement officials, including those who traveled or attempted to travel to Iraq and Syria, launched domestic attacks, or participated in recruiting or fundraising.

The Gorkas note in a new report that almost one third of these individuals had plotted attacks against Americans on U.S. soil in the last 18 months. Sebastian is also an adviser to the Department of Defense, while Katharine has authored several publications about the terrorist threat to the U.S. homeland.

Through Islamic State propagandists on Twitter and other social media sites, the terrorist group has been able to attract hundreds more supporters in the United States, they said.