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

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

The ship was on a routine patrol with other vessels in the Yellow Sea off South Korea's west coast. The exact cause of the explosion remained unclear and officials said it could take weeks to determine.

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 DPRK 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, the DPRK did not appear to be involved.

"We have detected 'no special movements' by North Korean forces," General Walter Sharp, chief of the 28,500 US troops in the ROK, said in a statement Sunday.

ROK troops were maintaining "solid military readiness," the Defense Ministry said. It also said a US military ship would join rescue operations Monday.

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. The ship then broke into two pieces, Defense Ministry officials said Sunday.

Military and coast guard ships and helicopters were searching the chilly waters Sunday.

Rescue ships retrieved about 20 life jackets and 15 safety helmets in waters 7-18 miles (11-29 km) away from the site, Joint Chiefs of Staff spokesman Park Seong-woo said.

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

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 at a naval base south of Seoul for the journey to the accident area as other relatives wailed in grief.

Officials will only be able to determine the cause of the explosion after the sunken ship is salvaged, a naval officer said Sunday.