North Korea could be making rapid preparations to carry out a nuclear weapons test for the first time in more than four years, a South Korean media report said, Taipei Times reports.

The Yonhap news agency, quoting government sources, said that North Korea appears to be digging a “shortcut” to Tunnel 3 at its previously closed nuclear test site in Punggye-ri.

Analysts at the Centre for Non-Proliferation Studies (CNS) had said earlier this month that satellite images showed signs of rebuilding at the site, but that getting it back up and running could take months or years. Now, North Korean leader Kim Jong-un’s administration might have changed its strategy.

North Korea “abruptly stopped its initial construction work to restore the entrance to Tunnel 3, and it is digging up the side [of the tunnel],” Yonhap quoted a source as saying, adding that it seems possible to restore the facilities within a month.

Punggye-ri is North Korea’s only known nuclear test site. It conducted six nuclear weapons tests in tunnels at the site from 2006 to 2017. North Korea’s last and largest nuclear test appeared to trigger geological instability that caused multiple small earthquakes, but analysts and US intelligence officials have said the site could probably be used again.

The development comes a few days after North Korea broke a UN ban and fired an intercontinental ballistic missile. Japan and South Korea said that it traveled 1,080km, reaching an altitude of more than 6,200km, coming down 145km west of Hokkaido, Japan’s northernmost island. Taipei Times