FBI Director James Comey said Friday that Islamic State-related investigations make up a majority of the 900 active investigations the bureau is carrying out nationwide into suspected homegrown terrorists, reports USA Today.

The FBI said the number also includes other extremists not related to the Islamic State group, but the vast majority of cases are looking into people inspired by the group who are suspected of plotting attacks or are heavily consuming the group's propaganda.

Comey warned that the number is "slowly climbing" as the Islamic State group continues to expand its reach into the U.S. by targeting young, discontented prospects through a social media campaign, according to CNN.

Comey and other FBI officials have previously mentioned there were "hundreds" of active investigations into people with suspected ties to the terrorist group, but official public references to specific numbers are rare, and this may be a first, according to the Inquisitr.

The pace of the investigations has varied over the past few months, and Comey suggested the FBI might not have enough resources to meet the mounting demand. Comey mentioned the July 4 holiday as an especially taxing period when the likelihood of an attack increases.

"If that becomes the new normal ... That would be hard to keep up," the director said, though he noted the pace has eased recently.

He also noted that the number of Americans attempting to travel to Syria to join forces with the Islamic State group has declined and said the bureau is not sure how that could affect domestic extremism.

"Something has happened that is flattening the curve (the number of travelers)," he said.

Comey also spoke Friday about the rise of violent crime in several cities across America. He linked the rise to police officers feeling more anxious due to the abundance of cellphone cameras and the "era of viral videos," which makes it more likely for law enforcement to be accused of misconduct, reported The Associated Press.

"I don't know whether this explains it entirely, but I do have a strong sense that some part of the explanation is a chill wind blowing through American law enforcement over the last year, and that wind is surely changing behavior," Comey said.