A white phosphorus spill inside the US Osan Air Base in South Korea prompted the Pyeongtaek city government to order nearby residents to evacuate on Tuesday afternoon, local officials said. No fatalities or injuries were reported, and the alert was withdrawn within hours after decontamination work, though accounts of the timeline differed.

The city dispatched an emergency text message at around 5 p.m. local time (08:00 GMT) urging people in adjacent areas to move to a safe location and avoid skin exposure, according to the Yonhap news agency. Police set up a cordon of 300 to 500 metres from the base, blocking pedestrians and diverting vehicles, South Korean media reported. The 51st Fighter Wing of the US Air Force said it established a 1,000-foot safety perimeter "due to a ground mishap and out of an abundance of caution," but denied reports of a wider evacuation of the base itself.

How long residents were told to stay away remains unclear. While the South Korean safety ministry and Yonhap described the evacuation order as being lifted after roughly half an hour, municipal text messages cited by ABC News indicated that the all-clear came several hours later. US Forces Korea did not provide additional comment on the timeline, and the base statement did not explicitly confirm a white phosphorus leak, referring instead to a munitions-related accident.

White phosphorus is a highly toxic and pyrophoric substance that ignites spontaneously on contact with air and causes deep thermal burns. Its military use is strictly regulated. South Korean police, fire and military authorities said they would investigate the cause of the incident; US officials assessed the leak as small in volume and not dangerous to public health or the environment, according to a Russian media report citing the base.