Two Filipino crew members of the "Stellar Daisy" have been rescued floating in a life raft on Apr 1, but other lifeboats and rafts found in the area were empty.
The "Stellar Daisy" had six lifeboats on board, two 30-seat lifeboats and four 16-seat lifeboats. The search operation is continuing for the 22 people.
South Korea has requested Brazil and Uruguay to assist in the SAR operation.
The ore carrier was sailing from Brazil to China carrying iron ore when it sent a distress signal to the ship operator on March 31.
A message last received by Polaris from a crew member said the ship was taking in water on the port side and was listing rapidly.
The master ordered all crew to put on lifejackets prior to capsizing.
The ship sank in less than five minutes in the vicinity of 34 04S 018 32W, 350 miles northwest of Tristan Da Cunha Island, and the EPIRB was activated automatically.
There were no other distress signals send from the ship itself after capsizing.
The signal was received by the Marshall Islands Marine Rescue Center (MRCC) at 11.52 p.m. on March 31 (Seoul time).
The initial distress signal was sent via messenger at 11.25 p.m. Omn Apr 1 at 03.54 a.m. and 03.57 a.m. there were two distress signals, sent via Distress Alert DSC, and those alerts could be sent by persons only, not automatically, from a position six miles off the EPIRB signal position.
Early reports suggested the vessel had lost stability and quickly sank. One report suggested the bulk carrier had capsized and sank. Another report suggested a cargo shift could explain the cause of stability. Cargoes like liquefied nickel have been documented to have caused ore bulk carriers to become unbalanced and suddenly sink.