North Korea has begun dismantling facilities at its nuclear test site, according to a satellite survey conducted by American researchers.
Analysts at the 38 North website say commercial imagery taken last week reveals that several support buildings have been demolished, railroads have been removed and mining carts overturned.
Pyongyang has promised to dismantle the Punggye-ri test site under the gaze of journalists between May 23 and 25.
The underground facility has been the site of all six North Korean nuclear tests.
The destruction of the site has been offered as an example of the secretive regime's commitment to disarming ahead of a historic meeting between Donald Trump and Kim Jong-un next month.
The commitment was praised by Moon Jae-in, the South Korean president, on Monday. "This would be a preliminary step toward complete denuclearisation," he said during a meeting with his aides, according to his office.
However, sceptics point out that part of the site is believed to have collapsed, rendering it unsafe, and that North Korean no longer needs a test site, having developed a nuclear arsenal.
The analysis suggests that work has already begun on dismantling the site.
Kim Jong-un has the USA and South Korea exactly where he wants them
"Imagery from May 7 shows that two key buildings (one likely an engineering office building, the other a compressor building) near the portal has been razed along with a shed that might have housed instrumentation equipment and one small outbuilding," reads the analysis.
"The rail lines for the mining carts have all apparently been removed and the previously noted train of mining carts appears to have been tipped over and/or disassembled on the spoil pile."
At the same time, a number of new structures may be designed to provide access and vantage points for the world's press.
However, no tunnel entrances at the test site appear to have been permanently closed yet.
North Korea’s nuclear progress - estimated yields per test
"This may be because on May 12, the official Korean Central News Agency announced that the final dismantlement of the Punggye-ri nuclear test ground would be witnessed by foreign journalists and would involve the 'collapsing all of its tunnels with explosions, blocking its entrances, and removing all observation facilities, research buildings and security posts'," the report concludes.