A mysterious North Korean facility may be producing components for building nuclear bombs, a new report suggests, offering clues to understanding the site near the capital that has perplexed experts and policymakers.The nondescript cluster of buildings called Kangson on the southwest outskirts of Pyongyang was first publicly identified in 2018 by a team of open-source analysts as the possible location of a facility for secretly enriching uranium, a fuel for nuclear bombs.But the report by North Korea watchers at the 38 North project, reviewed by Reuters before its release on Friday, says satellite imagery points to the facility making components for centrifuges, the high-tech spinners used to enrich uranium, rather than enriching the fuel itself."The characteristics of the site are more consistent with a plant that could manufacture components for centrifuges," writes former International Atomic Energy Agency (IAEA) official Olli Heinonen in the report.The imagery suggests the site lacks the infrastructure needed for enrichment, writes Heinonen, a distinguished fellow with the Stimson Center, the Washington think-tank that runs the project.Pyongyang has denied having secret nuclear sites, an issue that contributed to the failure of a 2019 Hanoi summit between US President Donald Trump and North Korean leader Kim Jong Un. Denuclearisation talks have remained stalled in part over US assertions that the North is not fully declaring the extent of its program."If the issue of undeclared facilities is going to be a factor in US-North Korea negotiations, as it was in Hanoi, the more we can learn about these suspected facilities, the better we can assess their role and value to North Korea’s overall nuclear weapons development," said Jenny Town, deputy director of 38 North.Friday's report could advance the debate on whether the Kangson site is building machines or using them to create bomb material.Clandestine enrichment sites would complicate efforts to estimate the number of nuclear weapons produced by the North, which has pushed ahead with enlarging its nuclear deterrent in the absence of a denuclearisation agreement.FILLING IN GAPSDavid Albright, one of the first analysts to reveal the site's existence, told Reuters it could be a covert enrichment facility but that the activity there is not convincing."We still see anomalies that do not allow us to reach a high confidence level" that enrichment is taking place at Kangson, said Albright, president of the Institute for Science and International Security in Washington.Similarly, a source familiar with US intelligence reporting and analysis told Reuters they have reasons to believe Kangson is enriching uranium but that the evidence is not conclusive.Kangson has many of features of an enrichment site, said Ankit Panda, a senior fellow at the US-based Carnegie Endowment for International Peace. It had been monitored by US intelligence for more than a decade before he and a team of imagery analysts at the James Martin Center for Nonproliferation Studies identified the spot in 2018, he wrote in a report at the time.The IAEA says Kangson shows some characteristics of an enrichment site but the organization cannot be sure, as North Korea expelled its inspectors in 2009.IAEA Director General Rafael Mariano Grossi told Reuters the UN watchdog has "indications," which he would not specify, that the site has a role in North Korea's nuclear program.Ramon Pacheco Pardo, a Korea expert at King's College London, said that "European intelligence officials are more cautious than their US counterparts" on whether Kangson is enriching uranium. The Europeans' position, he said, "is that we simply don't know what's going on there for sure, so they can't jump to the conclusion that enrichment is taking place without more solid evidence.”Friday's 38 North report attempts to fill in some gaps.Satellite imagery from 2003, when the main building was being constructed, shows a concrete floor that appears to be like those built for workshops, rather than the concrete pads used in enrichment facilities to protect sensitive equipment from vibrations, the report says.Kangson appears to lacking air conditioning units that are essential for enrichment plants, and its security perimeter is not as extensive as at other nuclear sites, Heinonen writes.He notes that the August UN report says an unnamed member state had spotted no cylinders used to transport uranium hexafluoride (UF6), a compound used in the enriching process.While commercial satellites might miss such transfers, he argues, it is unlikely that the intelligence services of foreign countries would fail to spot them.