The sailors went down with the 1,200-tonne Cheonan near the tense western sea border with North Korea shortly after it was ripped apart by what investigators believe was an underwater blast from outside the ship.
Fifty-eight sailors survived the sinking, but the bodies of six sailors remain unrecovered.
The South Korean defence minister has said a heavy torpedo was among the likeliest causes, although Seoul has not openly blamed North Korea pending the outcome of a multinational investigation by more than 100 experts.
|The bodies of six sailors killed in the disaster remain uncovered [AFP]
The seabed is still being scoured for any remnants that could confirm an attack on the Cheonan.
North Korea has denied involvement in the sinking.
The South's government is weighing its options for a response if it is proved that the North was to blame.
The disputed border in the Yellow Sea was the scene of deadly naval clashes in 1999 and 2002, and of a firefight last November which set a North Korean patrol boat ablaze.
An unidentified official told the Yonhap news agency that Seoul has not ruled out a military response if hard evidence emerges of Pyongyang's involvement, but it would likely take the case to the United Nations Security Council.
South Korea will brief permanent council members China and Russia on the outcome of its investigation, the official said.
On Wednesday, the United States said it is still committed to reviving the six-party talks on ending North Korea's nuclear programme despite suspicions over the North's involvement in the sinking of the warship.
"I wouldn't necessarily link those directly. And we want to see North Korea come back to the six-party process," Philip Crowley, a US state department spokesman, told reporters.
He also said any conclusion suggesting North Korean involvement will have wide ramifications.
"We're committed to this with our partners, but clearly provocative actions that North Korea takes have an impact on the broader environment."