North Korea's nuclear test site remains fully operational despite Pyongyang's announcement last week that it would shut down such facilities, a specialist website said on Tuesday. Although the so-called North Portal where North Korea had conducted five of its six atomic tests seems abandoned, the construction of new tunnels has been detected in another section at the Punggye-ri nuclear test centre, the website 38 North reported on the basis of satellite image analysis. The new tunneling was "curtailed by mid-March, but not entirely stopped through early April, suggesting that either the tunnel was complete and ready for future renewed testing or that the slowdown simply mirrored the ongoing political changes underway", Efe news quoted the website as saying. On April 21, the North Korean regime announced the immediate suspension of nuclear and intercontinental missile tests and closure of Punggye-ri. The 38 North website, linked to Johns Hopkins University, also said in its analysis on Tuesday that the nuclear base has another tunnel in the South Portal that can be used for future tests. It also rejected the opinions of some experts that North Korea had announced the closure of Punggye-ri taking advantage of the fact that the facilities might have been no longer viable after its last powerful nuclear test in September 2017. According to the analysis, "there is no basis to conclude that the Punggye-ri nuclear test site is no longer viable for future nuclear testing", since there remain two portal areas located in more pristine competent rock that can be used for future tests "if Pyongyang were to give the order". "Whether that will stay an option will depend on reaching verifiable agreements that build on Pyongyang's pledge to shut down the facility," the website added.