South Korean media continued to speculate Thursday about what caused the Cheonan warship to sink near the border with North Korea last week, as authorities called off efforts to find missing sailors for a second day due to weather.
Some reports cited satellite footage of a North Korean submarine disappearing and then reappearing around the time the Cheonan sunk last Friday as possible evidence of the North's involvement.
Officials, however, said the activity was normal. High-ranking military officials also dismissed as "unfounded" a claim by the head of parliament's defense committee that four North Korean semi-submersibles had crossed into South Korean territory, reports the Chosun Ilbo, a major daily.
The Kyunghyang Sinmun, an influential liberal newspaper, quoted experts raising the possibility that structural "fatigue failure" caused the ship to split in two. An explosion powerful enough to halve the 1,200 ton Cheonan would have been extremely loud, but no such sound was heard by guards or residents near the coast, the paper said.
Other reports said structural failure was extremely unlikely.
Investigating the possibility that a North Korean mine might have sunk the Cheonan, the South Korean Navy dispatched the Yang Yang and Woong Jin minesweeping vessels on Saturday, according to a Joint Chiefs of Staff official. The ships arrived near the scene of the incident late Sunday night.
"At the moment, there is not enough hard evidence to indicate the cause behind the Cheonan's sinking," says Mingi Hyun, a Korean-American research fellow at the Korea Institute for Maritime Strategy.
Mr. Hyun says the public will have to be patient until the Navy can examine the wreckage, which appears unlikely to happen until this weekend or next week.
"The continuing emergence of hypothetical scenarios has not helped clarify the picture," he adds.
Meanwhile, family members of the 46 missing sailors believed to be trapped inside the sunken stern of the Cheonan, a South Korean Navy patrol ship, criticized the Navy for mishandling the rescue effort.
They pointed to a shortage of equipment and decompression chambers for divers, and issued a joint statement asking the Navy to "do its utmost to save every last person."
About 207 South Korean divers are currently on-hand at the site, according to a JCS official. There are about two available chambers, but because ships are moving in and out of the area, the number is in flux, the official said.
He stressed that weather has been the main cause for the delay.
South Korean Navy diver Han Joo-ho, who died Tuesday, was brought aboard the USNS Salvor because the only available South Korean chamber was in use, according to Lt. A.J. Falvo, a spokesman for the 7th Fleet.
The Salvor came over from Japan to assist in the rescue effort, Falvo says. A 16-member US diving unit is standing by, but no American divers have yet entered the water, he adds.
"Current reports are calling for isolated thunderstorms, 5 ft. to 7 ft. seas and 35-knot winds, all non-conducive to safe diving operations. Divers will reassess the weather tomorrow and see if conditions are right," Falvo says.
Earlier Thursday, local time, President Barack Obama offered his "support and condolences" regarding the sinking of the Cheonan to South Korean President Lee Myung-bak in a phone conversation, according to wire reports.