North Korea's primary nuclear test site remains "fully operational" and could be used for further testing in the future, according to a report released Monday.

Monday's report comes after North Korean leader Kim Jong Un made the announcement on April 20 that his regime would cease its nuclear and long-range missile tests and close the mountainous Punggye-ri nuclear test site, where the regime has conducted all six of its nuclear tests.

Some experts have suggested that another test at the Punggye-ri nuclear test site could totally destroy it and potentially even cause a mountain to collapse.

North Korea's primary nuclear test site remains "fully operational" and could be used for further testing in the future, 38 North, a watchdog dedicated to analyzing the rogue state, warned Monday.

"North Korea’s Punggye-ri nuclear test site, where North Korea has conducted six acknowledged underground detonations is still, as far as we can tell, fully operational," 38 North reported.

Following North Korea's sixth nuclear test in September, commercial satellite imagery reportedly revealed significant tunneling in one area of the site up until early March. This activity appeared to slow down toward the end of March, but did not stop entirely into early April. According to 38 North, this suggests "that either the tunnel was complete and ready for future renewed testing or that the slowdown simply mirrored the ongoing political changes underway."

With that said, some experts have suggested another test at the Punggye-ri nuclear test site could totally destroy it and potentially even cause a mountain to collapse.

Monday's report comes after North Korean leader Kim Jong Un made the announcement on April 20 that his regime would cease its nuclear and long-range missile tests and close the mountainous Punggye-ri nuclear test site, where it has conducted all six of its nuclear tests.

"From April 21, North Korea will stop nuclear tests and launches of intercontinental ballistic missiles," the Korean Central News Agency said, according to the Seoul-based Yonhap News Agency. "The North will shut down a nuclear test site in the country's northern side to prove the vow to suspend nuclear test."

Kim's announcement was met with applause by President Donald Trump, who took to Twitter on Friday and described the move as "Progress being made for all!"

Trump is set to meet with Kim to discuss the rogue state's nuclear program in the near future, though on Sunday he tweeted, "We are a long way from conclusion on North Korea, maybe things will work out, and maybe they won't - only time will tell....But the work I am doing now should have been done a long time ago!" In a separate tweet on Sunday, Trump incorrectly claimed Kim's regime had "agreed to denuclearization" — North Korea has not indicated it will give up its existing nuclear weapons.

North Korea conducted a slew of long-range missile tests last year as part of its larger ambitions to develop a nuclear weapon capable of reaching the mainland US. This generated outrage across the international community and resulted in harsh economic sanctions being leveled against Pyongyang. But the tide began to shift in early 2018 as North and South Korea, historic enemies, renewed dialogue for the first time in roughly two years. This has also led to a cautious warming of relations between Pyongyang and Washington.