The U.S. Embassy in Kabul warned Americans trying to leave Afghanistan that they should be aware of “the potential of violence and security threats” near the airport. “We are processing people at multiple gates. Due to large crowds and security concerns, gates may open or close without notice. Please use your best judgment and attempt to enter the airport at any gate that is open,” the embassy said in a bulletin on Friday, adding that Americans need to watch out for “ongoing threats.” Several officials, including State Department spokesman Ned Price and Pentagon spokesman John Kirby, said on Thursday that they are not sure how many Americans are still in Afghanistan. However, President Joe Biden a day earlier confirmed between 10,000 and 15,000 U.S. citizens are still there, while tens of thousands more Afghans may try to leave on U.S. military flights. In its Friday bulletin, the U.S. Embassy again said …