Who knows what the truth is?

The US is monitoring intelligence that suggests North Korea's leader, Kim Jong Un, is in grave danger after undergoing a previous surgery, according to a US official with direct knowledge.

A second source familiar with the intelligence told CNN that the US has
been closely monitoring reports on Kim's health.

Kim recently missed the celebration of his grandfather's birthday on April 15, which raised speculation about his well-being. He had been seen four days before that at a government meeting.

Another US official told CNN Monday that the concerns about Kim's health are credible but the severity is hard to assess. 

Daily NK, an online newspaper based in South Korea that focuses on North Korea, reports that Kim reportedly received a cardiovascular system procedure on April 12. 

Kim received the cardiovascular system procedure because of "excessive smoking, obesity, and overwork," according to the news site, and is now receiving treatment in a villa in Hyangsan County following his procedure.

After assessing that Kim's condition had improved, most of the medical team treating him returned to Pyongyang on April 19 and only part of them remained to oversee his recovery situation, according to the news site. CNN is unable to independently confirm the report.

A South Korean source told CNN Monday that the country's top leaders are very much aware of reports about Kim's health status but cannot independently verify details published by Daily NK. The source acknowledged that Kim's issues related to weight and smoking are well known but made clear they are waiting for more information. 

South Korea's Presidential Blue House said in a statement provided to reporters that they have nothing to confirm on reports about Kim's health and that "no unusual signs" have been detected inside North Korea.