BAENGNYEONG ISLAND: Weeping, angry relatives of 46 crew members missing after a mysterious explosion sank a South Korean navy ship sailed around the site Sunday as rescue teams took to the air and sea still hoping to find survivors.

None have been found since an initial rescue of 58 sailors from the 1,200-ton Cheonan that sank near the tense border with North Korea early Saturday. No bodies have been discovered.

The exact cause of the explosion late Friday remained unclear — and officials said it could take weeks to determine. The ship, which was on a routine patrol with other vessels in the Yellow Sea off South Korea's west coast, sank about three hours after the blast.

It is one of South Korea's worst naval disasters. In 1974, a ship sank off the southeast coast in stormy weather, killing 159 sailors and coast guard personnel. In 1967, 39 sailors were killed by North Korean artillery.

Fierce waves and high winds have hampered the search in the area where the two Koreas have fought bloody naval engagements. Despite the location of the sinking, North Korea did not appear to be involved.

The explosion tore open the rear hull of the Cheonan, shut down its engine, wiped out power and caused the ship to sink a little over three hours later, according to the Joint Chiefs of Staff.

Military and coast guard ships and helicopters were searching the chilly waters Sunday, South Korea's navy said.

The weather conditions had improved from Saturday, but Yonhap news agency reported that dozens of military divers quickly withdrew due to rapid sea currents. Divers also unsuccessfully tried to get to the wreckage on Saturday.

President Lee Myung-bak ordered officials to "thoroughly investigate" the sinking and make their best efforts to rescue any possible survivors, according to his spokesman Park Sun-kyoo.

As hopes faded for the missing crew, about 80 family members aboard a navy patrol boat sailed around the site and watched rescue operations.

"My Son! My son!" one crying woman shouted while boarding the ship late Saturday at a naval base south of Seoul for the overnight journey to the accident area as other relatives wailed in grief.

The family members were to return later Sunday to a naval base south of Seoul, where other relatives awaited news.

Though there was no indication North Korea was to blame, South Korean troops were maintaining "solid military readiness," the Defense Ministry said.

North Korea lies within sight about 10 miles (17 kilometers) from Baengnyeong. The Koreas remain in a state of war because their three-year conflict ended in a truce, not a peace treaty, in 1953.

Officials could determine what caused the explosion only after the sunken ship is salvaged, a naval officer said Sunday. The officer, speaking on condition of anonymity citing department policy, said it's expected to take about one month to salvage a ship of that size.

A survivor, Staff Sgt. Shin Eun-chong, 24, told relatives Saturday that he was on night duty when he heard a huge boom behind him that split apart the ship. The vessel started tilting, and his glasses fell off his face as he hit the deck, relatives at the naval base in Pyeongtaek told The Associated Press.

Some families also vented anger at the military, accusing authorities of a cover-up and saying survivors told them the Cheonan was leaky and in need of repair. They shouted "Liars!" and jumped on a car of carrying the rescued captain of the Cheonan as it drove away.

As family members scuffled with guards, some soldiers turned their guns onto the protesting relatives.

"I find this gruesome reality — one where soldiers point their guns at heartstricken families of their comrades in arms — absolutely devastating and regrettable," said Chung Hae-kyung, 65, father of a missing lieutenant.