As tensions between Kim Jong-un and President Donald Trump remain high, China is building refugee camps along its 880-mile border with North Korea in preparation for a conflict or political upheaval that would result in a mass resettlement.

The news of China’s plans for refugee camps was first reported by the Financial Times, which obtained leaked documents from China’s largest mobile phone company revealing the plans. The documents said that the company was testing signal strength at five sites designated as “refugee settlement points.”

The leaked documents which went viral on social media, but were later deleted by Chinese authorities, read:

“Due to cross-border tensions … the [Communist] party committee and government of Changbai county has proposed setting up five refugee camps in the county.”

The document named three of the sites: Changbai riverside, Changbai Shibalidaogou and Changbai Jiguanlizi.

According to the Guardian, a spokesman for China’s foreign ministry refused to confirm the existence of the refugee camps at a press briefing on Monday.

Tensions have risen between North Korea and the United States, in the wake of Pyongyang’s November 29 intercontinental ballistic missile test which the regime said proves that it could reach targets anywhere on U.S. soil.

In a sign of China’s uneasiness, an official newspaper in Jilin, China, located near North Korea’s nuclear test site, ran a full-page article on how to deal with a nuclear incident, the Guardian reported. Readers were urged to have iodine tablets, masks, and soap in case of such an eventuality.