Kurdish-led forces in Syria, allied with the United States, shot down an Air Force MQ-9 Reaper drone on Monday after mistakenly identifying it as a threat.

Troops from the Syrian Democratic Forces, a key ally for the United States in its fight against the Islamic State, were conducting operations in the region when they downed the MQ-9, a U.S. official familiar with the situation confirmed to Defense News.

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The MQ-9 was operating over Syria to support the campaign against the remnants of the Islamic State, known as Operation Inherent Resolve.

U.S. forces recovered the parts of the drone that needed to be salvaged and destroyed the rest, the official said.

“U.S. Air Forces Central [Command] is actively assessing the actions that led to the incident and will adjust tactics, techniques and procedures to safeguard U.S., coalition, and partner forces and their associated assets,” the official said.

The SDF’s position in Syria has grown precarious in the days since the ouster of President Bashar Assad. Turkey, which borders Syria to the north, has accused the SDF of having ties to the Kurdistan Workers’ Party, or PKK, which Turkey views as a terrorist group.

The Telegraph reported the Turkish-backed Syrian National Army began advancing toward the Syrian Kurdish-controlled city of Manbij earlier this week, before the U.S. helped broker a ceasefire between the SNA and SDF.

U.S. forces, including B-52 Stratofortress bombers, A-10 Warthog attack planes and F-15 fighters, pounded 75 ISIS targets in dozens of strikes shortly after the rapid fall of the Assad regime.