The State Department said Sunday that it doesn’t have the “reliable means” to back up a claim that flights carrying American citizens meant to leave Afghanistan were stopped from taking off by the Taliban.

Rep. Michael McCaul, R-Texas, who serves as the top Republican on the House Foreign Affairs Committee, said Sunday that six airplanes have been blocked by the Taliban from leaving Mazar-i-Sharif International Airport in northern Afghanistan.

McCaul also said the Taliban is holding the Americans hostage but provided no details about what the terror group wanted in return, and that the flights had been cleared by the State Department, according to The Hill.

A State Department spokesperson said that since there are no personnel or air assets in the country and no airspace in the region, the Department cannot confirm details of the charter flights, telling The Hill that “[G]iven these constraints, we also do not have a reliable means to confirm the basic details of charter flights, including who may be organizing them, the number of U.S. citizens and other priority groups on-board, the accuracy of the rest of the manifest, and where they plan to land, among many other issues.

“We understand the concern that many people are feeling as they try to facilitate further charter and other passage out of Afghanistan,” the agency said. “As with all Taliban commitments, we are focused on deeds not words, but we remind the Taliban that the entire international community is focused on whether they live up to their commitments.”

A number of American citizens still remain in Afghanistan, after the U.S. completed its troop withdrawal.