A total of 58 people were rescued from the bow section of the ship soon after the sinking but another 46 crew members had been missing since the disaster.
Efforts to locate the missing crew have been hampered by bad weather and strong currents.
A week after the disaster, officials are still searching for answers as to what caused the ship to break in the murky waters off Baengyeong Island.
Defence ministry and presidential officials have dismissed media reports that the ship had been tracking North Korean submarines at the time.
|The S Korean Cheonan sank near the disputed Yellow Sea border with N Korea [AFP]
Kim Tae-Young, South Korea's defence minister, said on Friday a torpedo might have sunk the warship but did not indicate who might have fired one.
Seoul has not cited any evidence the North was involved, although the defence minister earlier in the week said a North Korean mine - either drifting or deliberately placed - might have caused the disaster.
South Korea's navy, backed by fishing boats and US military divers, has been struggling against high waves and strong currents to explore the hull sections of the sunken warship where many of the missing sailors could have been trapped.
Divers have entered the mess hall at the rear of the ship and examined the captain's chamber and communications centre in the broken wreckage of the sunken ship.
Attempts to go deeper inside the hull were made difficult by wires and debris detached from the ceiling and walls, navy officials said.
Most of the missing are suspected to be in the rear section of the hull.
The missing sailors have not officially been declared dead, although any air in the ship's watertight compartments would likely have been used up.
The area where the warship went down has been crowded with ships and aircraft, which have been combing the area in a search and rescue operation.
Two sailors died and seven were missing on Saturday after their fishing boat, which had been helping in the search, collided with a freighter, Yonhap said, quoting the Incheon Coast Guard.
The disaster site is close to the disputed border which was the scene of deadly naval clashes between North and South Korea in 1999 and 2002 and of a firefight last November.