Seoul, South Korea (CNN) -- Strong winds and rough waves Sunday dimmed hopes of rescuing 46 South Korean sailors as search efforts entered their second day following the Friday night sinking of their navy ship off the North Korean coast.
South Korean rescuers continued to scour the Yellow Sea on Sunday for the missing sailors from the patrol ship Cheonan, according to the Yonhap News Agency.
"We are hoping to be able to go underwater today," a military official said, according to Yonhap. The news agency said that military divers failed Saturday to reach the sunken vessel.
The ship was carrying 104 sailors, 58 of whom have been rescued. No bodies or survivors have been found in the sea. No cause has been determined for the ship's sinking, although Yonhap has quoted military officials as saying that an unidentified explosion tore a hole in the ship's rear, shutting off the engine and sinking the ship in fewer than three hours.
After visiting the site, Defense Minister Kim Tae-young told the media Saturday that the vessel appears "to have been split into half."
However, he said making predictions "is meaningless. ... Please bear with us."
A photograph released to media showed a section of the ship's hull still above water, raising hopes that the sailors could be alive.
The navy plans to salvage the sunken vessel to determine what caused the incident, Yonhap reported. It was carrying missiles and torpedoes, Yonhap reported, quoting navy officials.
South Korean President Lee Myung-bak has ordered a "quick and thorough" investigation into what caused the ship to sink, keeping in mind "all possibilities," his office said, according to Yonhap. President Lee met with security officials on Sunday, but the government did not offer new information on the missing sailors.
Families of the missing sailors stormed the Pyeongtaek naval base south of Seoul on Saturday afternoon demanding information.
Given Baengyeong island's proximity to North Korea, North Korean involvement was feared, but South Korean officials have played down that scenario. And U.S. State Department spokesman P.J. Crowley said Friday that there was no evidence North Korea was behind the incident.
Baengnyeong residents had reported hearing gunfire at sea shortly after the Cheonan sank. South Korean officials later confirmed that one of their ships had fired on a radar contact that turned out to be a flock of birds.
Presidential spokeswoman Kim Eun-hye told reporters there were "no unusual signs" of North Korean activity near the scene. North Korean state media remains silent on the issue.
Baengnyeong, a Seoul-administered island, lies on the Northern Limit Line (NLL), the maritime border between the two states which North Korea disputes and which covers rich crab fishing grounds.
The NLL was the scene of fatal naval skirmishes in 1999 and 2002. The two Koreas also exchanged naval gunfire in 2004 and 2009. In recent months, North Korea has been firing coastal artillery into the waters near the island, and shells had been fired earlier Friday, according to news reports.
In 2003, a salvage operation to lift a capsized patrol boat -- a vessel much smaller than the 1,200 ton Cheonan -- took 17 days. That patrol vessel was capsized after a gunfight with North Korean naval units.
Journalist Andrew Salmon contributed to this report