A white phosphorus leak accident was reported at a US air base in South Korea on Tuesday, prompting the local authorities to issue an emergency alert to nearby residents, according to Yonhap news agency.

It was reported to the police at about 5:07 p.m. local time (0807 GMT) that white phosphorus had leaked at the K-55 base, also called Osan Air Base, in Pyeongtaek, a city around 65 kilometers south of the capital Seoul that hosts a major US military presence.

In response, the Pyeongtaek municipal government sent an urgent text message to residents, saying that residents in surrounding areas are advised to evacuate to a safe place to avoid skin exposure as white phosphorus was leaked inside the K-55 US military base.

No casualties had been confirmed yet, according to local media.

White phosphorus is a highly toxic and volatile chemical substance, which ignites spontaneously upon contact with air and causes severe burns and issue damage upon skin contact.

The police, the fire authorities and the military planned to investigate the exact cause of the incident.