U.S. government and military officials are concerned about the possibility of a second terrorist attack in or around the Hamid Karzai International Airport, where troops are working to evacuate Americans and Afghan allies who would be in danger under the Taliban regime.

Pentagon spokesman John Kirby described “specific credible threats” against the U.S. forces stationed at the airport during Friday’s morning briefing, approximately 24 hours after an ISIS-K operative detonated a suicide vest killing more than a dozen U.S. soldiers, more than 100 people in all, and wounding countless others.