Muslim-American terror in 2015 reached its highest point since the September 11, 2001 attacks against America, the Triangle Center on Terrorism and Homeland Security (TCTHS) said in a report released Tuesday, documenting that 81 Muslim-Americans were associated with terror plots in the past year.

The report also documented that 41 additional Muslim-Americans over the past three years have traveled to Syria in order to join Islamic militants.

Since 9/11, 344 Muslim Americans have been involved in “violent extremism,” the terror research document said. “Half of these individuals plotted against targets overseas; 10 percent involved unknown targets; and 40 percent plotted against targets in the United States,” the report adds.

The Triangle Center’s research said of Americans who joined the jihad abroad:

According to court records, media reports, and social media postings, 41 Muslim-Americans have joined the self-proclaimed “Islamic State” in Syria, Iraq, or Libya, or the Nusra Front (Jabhat al-Nusra), al-Qaeda’s franchise in Syria, since the Syrian civil war broke out in 2011. Twenty of these Americans have died, while 16 (11 men and five women) appear to be living in territory controlled by these groups. Five were arrested after their return to the United States; of these, one (Abdirahman S. Mohamud) was accused of planning an attack in the United States.

Duke University professor David Schanzer, who directs the terrorism research institute, said the U.S. government “estimates that 250 Americans have traveled to fight in Syria.”

Another one of the professors involved in the study, however, appeared to dismiss the troubling results of his own study, instead highlighting mass shootings as a more serious problem.

“Fortunately, the appeal of revolutionary violence remains very limited among Muslim-Americans,” said Charles Kurzman, a UNC professor and author of the report. “Muslim-American extremists have caused 69 deaths over 14 years, while 134 people were killed in mass shootings in the United States in 2015 alone.”

The Triangle Center on Terrorism and Homeland Security is a collaborative research center run by experts and scholars from Duke University, the University of North Carolina at Chapel Hill, and RTI International.

Read the full report here