Seoul, South Korea (CNN) -- Two North Korean sailors are dead and 11 missing after a Mongolia-flagged cargo ship sank off the southeastern coast of South Korea.
Three sailors were rescued by the South Korean Coast Guard after the distressed ship, Grand Fortune 1 sank early Friday.
"The sunken ship sent the rescue signal at around 1:19 a.m. from some 130 kilometers away and took two hours to reach," said Kang Byung Moon, the director of public affairs at the Yeosu Coast Guard.
South Korean officials deployed a search plane and a patrol ship to find survivors and rescued the first sailor around 5 a.m.
"Because he suffered from hypothermia, we could not get any information until he came around to find out that he was from North Korea and that there were 15 others on board," Kang said.
The other two survivors were rescued at 5:55 a.m. and 7:12 a.m. respectively. The three survivors are being treated on Jeju island, according to South Korean government officials.
It remains unclear why the cargo ship sank.
The ship was believed to have be coming from Chongjin in North Korea, headed to China, reported Yonhap, South Korea's semi-official news agency.
It carried a Mongolian flag, but had an all-North Korean crew. The two countries are traditional allies and North Korea has been known to sail rented ships.