The U.S. Air Force reversed its initial assessment of residue found at Osan Air Base in South Korea, stating laboratory tests showed the material was nonhazardous corrosion, not white phosphorus.

The residue was discovered during a routine munitions inspection on July 28, 2026, at Osan Air Base, which hosts the 7th Air Force and 51st Fighter Wing near Pyeongtaek city.

Initially described as white phosphorus, a hazardous substance, the material triggered emergency notifications and a temporary evacuation advisory from the city, which was withdrawn after 37 minutes. No injuries occurred, and base operations continued normally. The wing said layered protection protocols were used for containment.

The wing emphasized safety as a priority and thanked local authorities for their cooperation.