American analysts said that commercial satellite images demonstrate that construction is underway at the nuclear test site in North Korea, which was closed in 2018.

Satellite images taken last Friday indicate early signs of activity at the new facility, including the construction of a new building, the repair of another building and possibly lumber, according to experts from the California James Martin Center for Nonproliferation Studies(CNS).

“Construction and repair work indicate that North Korea has made some kind of decision on the status of the landfill,” the statement said.

Punggye-ri was closed after North Korea declared a moratorium on nuclear weapons tests in 2018. However, the country’s leader, Kim Jong-Un, said that he no longer considers himself bound by this moratorium, since negotiations on denuclearization have reached an impasse.

After North Korea’s ninth ballistic missile launch this year, South Korea’s National Security Council said it was monitoring North Korea’s nuclear and missile facilities even more closely, including its main nuclear reactor in Yongbyon and the Punggye-ri nuclear weapons test site.

CNS analysts said that the changes in Punggye-ri have occurred only in the last few days, and it is still difficult to conclude what exactly is being built and why.

“It is possible that North Korea plans to bring the test site into a state of readiness for the resumption of nuclear tests,” the report says.

CNS analysts have warned that the test site will be ready for new nuclear tests in months, and possibly years.

“How long it will take North Korea to resume testing at this facility depends on the degree of damage to the tunnels themselves destroyed earlier, which we do not know with certainty,” CNS said in a statement. “It is also possible that North Korea will resume nuclear tests elsewhere.”

Punggye-ri is the only known nuclear test site in North Korea.

The United States says it is open to talks without preconditions, but North Korea says Washington and its allies must first end their “hostile policy” towards Pyongyang.