A Mongolian-flagged freighter with a crew of 16 North Koreans sank off the coast of South Korea, killing at least two, the South’s coast guard said.

The “Grand Fortune” was carrying iron ore from North Korea to China when it sank 130 kilometers (81 miles) off the southern South Korean city of Yeosu early this morning, the Korea Coast Guard said in a statement. Three crew members were rescued and 11 are missing, it said.

The Korea Coast Guard did not detail a cause of the sinking. Waves were as high as 3.5 meters (11 feet) in the area around the time of the incident, which occurred outside South Korean territory, it said.

“The lives of the rescued people are not at risk,” the coast guard said. Footage of the incident posted online by the coast guard showed one crew member being pulled from the water by a helicopter, wearing a life vest inscribed “Ulan Baatar,” the capital of Mongolia.

Last month, South Korea repatriated a North Korean fishing boat that drifted across the disputed western maritime sea border with engine trouble. The two countries remain technically at war after the 1950-53 Korean War ended without a peace treaty.