And there's now extra focus on whether there are indeed more nuclear and missile facilities in North Korea than the well-publicized Yeongbyeon nuclear facility.
Lee Seung-jae reports.

The second and final day of the Hanoi Summit between the leaders of North Korea and the United States fell apart around lunchtime,... with neither side agreeing to a deal.
The main bone of contention seems to be the fact that North Korea has other nuclear testing locations other than its Yeongbyeon site.
During his post-summit press conference, President Trump said North Korean leader Kim Jong-un was caught off guard when the U.S. delegation mentioned the regime's other testing sites.
One of the sites in question,... suspected of being a uranium enrichment plant, is a complex located in Kangsong ,... just southwest of Pyeongyang,... along the Daedonggang River.
The site was one of about 20 detected by satellite,... according to Stanford University's Center for International Security and Cooperation.
CNN reports Kim pushed for the removal of sanctions with the elimination of the Yeongbyeon complex as his main leverage,... however, he was unaware the U.S. already knew about the other facilities.
Pundits say the break down of the summit could have a big impact on the North Korea-U.S. relationship in the near-term,... as it remains unclear whether the Trump administration will seek to reopen negotiations with the regime in the near future.
Lee Seung-jae, Arirang News.