Addressing intelligence officials on Friday, FBI Director James Comey delivered a stunning estimate of 900 investigations currently in progress against suspected ISIS operatives, recruits, and individuals “inspired” by the Islamic State, and the number of investigations is slowly growing.

USA Today notes it is rare for FBI officials to discuss the number of investigations in this way. Comey seems to have disclosed the number in order to buttress his case that the Bureau is finding it very difficult to keep up with the anti-ISIS caseload. Referring to a particularly intense period of counter-terror activity around the Fourth of July, Comey warned, “If that becomes the new normal… that would be hard to keep up.”

Comey noted the number of Americans defecting to ISIS has decreased recently, though admitted to not being certain why this is the case—perhaps the significant number of recruits, thwarted by the FBI in their efforts to make the journey to the Middle East, has made others more cautious about trying it, as such, arrests make big news headlines. It could also be growing more difficult for the Islamic State to secure passage for its recruits into Syria.

However, USA Today ominously notes it is “unclear” how the drop-off in ISIS recruits leaving the country “may be affecting the domestic threat.” If the number of ISIS investigations is growing, but the number of recruits leaving the country is declining, it is natural to worry that means more dangerous individuals loyal to the Islamic State and its murderous ideology are plotting violent acts on American soil.

Comey seemed inclined to view the reduction in ISIS recruits departing for the Middle East as good news in testimony before the House Homeland Security Committee earlier this week.

“We’re starting to notice that curve, which was going up like a hockey stick, has flattened a little bit,” the FBI Director said on Wednesday, as reported by The Hill. “We are seeing fewer people attempt to travel to join ISIL in Syria.” He characterized the rate as dropping from roughly nine departures per month, to only six over the past three and a half months.

He also allowed for the possibility that ISIS recruits are still making the trip to Syria but have developed means of doing so without getting caught.

Comey also addressed the danger of trained terrorist recruits returning to the United States after serving abroad in the ISIS military. He described it as an issue the FBI planned to watch “for the next five years plus,” because “inevitably, there will be a terrorist diaspora out of the so-called Caliphate.”