With just a few days remaining before its own deadline, the U.S. military mission to evacuate American civilians has hit a snag—an imminent threat to Americans trying to leave through the Kabul airport.

Late Wednesday, the U.S. Embassy in Kabul issued a security alert that reads:

Because of security threats outside the gates of Kabul airport, we are advising U.S. citizens to avoid traveling to the airport and to avoid airport gates at this time unless you receive individual instructions from a U.S. government representative to do so.

The State Department echoed the message.

#Afghanistan: Due to threats outside the Kabul airport, US citizens should avoid traveling to the airport and avoid airport gates unless you receive instructions to do so. Those at the Abbey Gate, East Gate, or North Gate now should leave immediately. https://t.co/InzuVjXhLT pic.twitter.com/6ncsJBEVLu

— Travel – State Dept (@TravelGov) August 25, 2021

The New York Times writes:

The British and Australian governments issued similar warnings, with Australian officials describing “an ongoing and very high threat of terrorist attack.”

The warnings came as the last of the estimated 1,500 Americans still in Afghanistan try to make it to the airport to leave before the U.S. withdrawal on Aug. 31. Tens of thousands of Afghan nationals are camped outside the perimeter of the airport in desperate attempts to escape on the last flights out.

No details were shared as to what prompted the warning or when it may be clear to travel again.