U.S. authorities this year have arrested nearly five dozen people in the United States for helping to support or plot with the Islamic State in Iraq and the Levant, according to a new study, the largest number of terrorism-related arrests in the country in a single year since September 2001.

ISIL recruits defy any single profile, the study found, although they are younger than previous terrorism suspects, are drawn heavily from converts to Islam and reflect increasingly prominent roles for women in the group.

A snapshot of the 71 individuals arrested on ISIL-related charges since March 2014, including 56 this year, emerged from a review conducted by the George Washington University.

The volume and diversity of those arrested underscore the growing challenge the FBI and local law enforcement agencies face in trying to identify, monitor and, if necessary, apprehend suspects at a time when ISIL has sharply increased its appeal to Westerners through social media.

“The diversity is staggering,” said Lorenzo Vidino, director of the university’s program on extremism.

The report was made public Tuesday.

Officials said that 80 percent of those arrested on terror charges in the past 18 months were younger than 30 and 40 percent were under 21. About 14 percent of those arrested were women. Since July, an average two Americans a month have tried to travel or successfully traveled to ISIL territory, compared with nine a month the previous year.

New York Times