The emergence of roughly one thousand women and girls who have escaped the clutches of the Nigerian extremist group Boko Haram as government forces put pressure on areas it once controlled does not mean the terror group has become debilitated, U.S. intelligence officials and experts told The Daily Beast.

Images of the women and girls emerging from captivity, where some were forced to marry members of the group and may have been impregnated, raised hopes that Boko Haram was in its final throes, just two months after a regional coordinated military effort wrested territory away from the militants. But despite the welcome news, officials and experts warned that Boko Haram has still successfully carried out terror attacks even after experiencing losses. And while the group no longer controls the northwest region of Nigeria, state forces don’t hold the area either, leaving it a large ungoverned space.

That the group no longer holds that territory “is not necessarily a defeat. It could be a tactical maneuver,” one U.S. intelligence official explained to The Daily Beast. “Are the women and girls being released? Or did Boko Haram walk away?”

Nigerian forces have moved slowly through former Boko Haram territory, which is dense and riddled with traps. Hundreds of captives have reemerged—and in some cases have been reunited with their families. But there are not similar numbers of Boko Haram members being captured by the Nigerian military from their former territory. Rather it appears terror group members have blended in with the population.

“We are not getting reports of large numbers of Boko Haram being captured. They kept their prisoners as long as they could, and the fighters are slinking away,” said J. Peter Pham, director of the Africa Center at the Washington-based Atlantic Council.

Moreover, Boko Haram’s declared allegiance to the self-proclaimed Islamic State could mean the Nigerian group’s leader, Abubakar Shekau, will be more receptive to outside funding and support. “They are still an insurgency. And they can evolve very quickly into a terrorist organization,” Pham said.

At its peak, the group controlled more than 30 towns, up from one just a year ago, much of it in the dense Sambisa forest. Earlier this year, a coalition of forces from Chad, Niger, and Cameroon helped Nigerian forces wrest control away from Boko Haram in nearly each of those towns, prevailing in just weeks. It was an unexpected, sweeping defeat for a group that had successfully fended off the beleaguered Nigerian government, all while taking new land, for the past year.

In the initial weeks after the end of the campaign, Boko Haram was notably quiet. Nigeria’s presidential elections at the end of March occurred without major attacks, which many feared, raising hopes the terror group had been defeated.

But in the last two weeks, deadly Boko Haram attacks have started again. In Niger, at least 74 people were killed on Lake Chad’s Karamga Island when Boko Haram fighters ambushed civilians there on April 25. It was the deadliest attack Niger had suffered since it began its campaign against Boko Haram in neighboring Nigeria and led officials there to call for the evacuation of at least 4,000 displaced Nigerians.

“I think it is premature to rule them out. They are in very bad straits, militarily. But even deprived of their territory they are still capable of attacks,” Pham said.

How many more women, girls, and other Boko Haram hostages could emerge remains a mystery as the group spent years taking hostages to an area that remained largely out of government control. According to an April 2015 Amnesty International report, at least 2,000 women were kidnapped since 2014 alone. In addition to women and girls forced to become sex slaves to their captors, Boko Haram also took young men and forced them to become fighters. In addition, the group snatched upper- and middle-class Nigerians in exchange for ransom.

The women and girls were most often held in large camps together, military bases and houses.

“We know there have been thousands that have been taken over the last few years. The question is how many are still alive,” Pham said. “Sometimes, when they couldn’t take them, Boko Haram killed them.”