More than 200 Americans have traveled or attempted to travel to Syria to fight with Islamic State militant groups in the country, FBI Director James Comey Said Wednesday.

"We continue to identify individuals who seek to join the ranks of foreign fighters ... and also homegrown violent extremists who may aspire to attack the United States from within," Comey told lawmakers on the Senate Select Committee on Intelligence, according to Reuters.

The number of Americans who joined ISIS in Syria is still a fraction of the number of Europeans who have done so. Gilles de Kerchove, the European Union’s counterterrorism chief, estimated last month that around 4,000 Europeans had joined the group.

In addition, Comey told senators that the threat posed by groups such as the so-called Islamic State warranted a “debate” about limiting commercial encryption technology, which he said assisted militant groups in recruiting Americans to their cause.

“There is simply no doubt that bad people can communicate with impunity in a world of universal strong encryption,” Comey wrote in a blog post published earlier this week.

Comey argued that technology companies could invent new methods of encryption that would allow U.S. law enforcement and intelligence agencies to track militants without introducing security flaws. Security experts, however, have not been receptive to the idea, with cybersecurity expert Susan Landau accusing Comey of “magical thinking,” the Guardian reported.

Earlier this year, Comey warned that "hundreds, maybe thousands" of Americans were being groomed by ISIS via messaging and social media, in an attempt to recruit them to fight in the Middle East or carry out attacks in the U.S., USA Today reported.

Since the thwarted attack on a "Draw Muhammad" conference in Garland, Texas, on May 3, the Justice Department has announced the arrests of 10 individuals it says were inspired by and supporting the Islamic State, according to Bloomberg.

Congressional leaders and the Justice Department cited by the agency said last month that the FBI was shifting its approach toward targeting individuals thought to be planning attacks in the U.S., unlike its past focus on volunteers preparing to join ISIS abroad.