Hardly there is information available on Kim Jong-un's nuclear arsenal, other than what North Korean controlled media has released on it.
The detention comes amid heightened tensions between North Korea and the US. The university said it could not comment further because Kim's detention was not related to his work at the university.
Speaking to the VOA Korean Service on Sunday, Kim Mi Ok said her husband was arrested as he tried to return to the couple's home in Dandong, China. "I waited until the train doors closed, but I couldn't find him", Kim said.
According to a message by Kim Hak Song dated February 2015 on the website of a Korean-Brazilian church in Sao Paulo, Kim was a Christian missionary planning to start an experimental farm at PUST and was trying to help the North Korean people learn to become self-sufficient.
"That does not mean, however, that the detainees will not be part of that dialogue because I - from my experience, I would say one of the first requirements we would have is to show goodwill". DPRK is short for the Democratic People's Republic of Korea, North Korea's official name. PUST is North Korea's only privately funded university and has a large number of foreign teachers, including Americans.
The Yalu River Bridge links Sinuiju, in North Korea's North Pyongan province with Dandong, a prefecture-level city in China's Liaoning province, and accounts for more than half of the Pyongyang's trade volume with Beijing.
Trump has said he would be open to meeting with Kim "under the right circumstances".
If Beijing does shut down the bridge, the move is expected to seriously damage the economy of North Korea, which relies on China for more than 90 percent of its exports.
US again warns against travel to NKorea after new detentions
In a statement, the U.S. State Department said, "The security of U.S. citizens is one of the department's highest priorities".
Tony Kim - or Kim Sang Dok - also a PUST staffer, was arrested on April 22 at an airport in Pyongyang on charges of "hostile acts" toward the regime.
Washington said it was "aware of reports that a U.S. citizen was detained in North Korea" and would liaise with Pyongyang. In 2015, trade between the two countries reached USA $5.4 billion.
The U.S. has not been tacit during Pyongyang's continuing firestorm.
The other is Otto Warmbier, a University of Virginia student who was detained for trying to steal a propaganda sign from a Pyongyang hotel on New Year's Day 2016 while on a group tour.
Korea studies professor Stephan Haggard of the University of California San Diego described these two recent arrests as "classic asymmetric warfare", to Time magazine, with North Korea "nabbing" American citizens in response to pressure against its nuclear and missile programs.
Israel's Netanyahu says Palestinians don't educate to peace
Militant Palestinian group Hamas has elected a new leader , further hinting the organization is trying to soften its image. Hamas has announced a new leader of its Qatar-based wing, in a significant win for the Gaza-based faction of the group.