South Korean Navy teams have located the wreckage of a patrol vessel that sunk Friday after an apparent explosion.  Even as hope dims, the search for survivors, and an explanation, goes on.

Naval rescue teams have located the hull of the vessel, which went down near a disputed maritime border with North Korea.

South Korea's government insists it will keep trying to find survivors of Friday's accident in waters west of the peninsula, despite indications a race against time may be coming to an end.

Rear Admiral Lee Ki-Shik, with South Korea's Joint Chiefs of Staff, says no survivors were found Monday.

Lee says divers reached the hull of the ship and knocked on it for several minutes, but heard no response.  He says the divers' time was limited by their oxygen supply, and that the day's efforts would be ending soon due to disappearing sunlight and visibility.

Fifty-eight of the 104 sailors aboard the vessel were rescued Friday.  Relatives of the missing 46 have vented anger at the government for what they describe as a lack of transparency in its response to the sinking.

If anyone was trapped on the ship, South Korean officials estimate there may be enough oxygen in watertight compartments for them to survive for as long as 69 hours.  

The ship sank in one of the world's tensest maritime regions, where Pyongyang has long disputed a U.N.-mandated sea border.  South Korean officials say it is unlikely North Korea attacked the ship.

South Korea's Defense Minister told lawmakers it is also unlikely the ship made contact with a South Korean mine.  They have not yet ruled out the possibility the ship hit a North Korean mine, possibly unaccounted for from the 1950s Korean War.

Meanwhile, North Korea threatened "unpredictable incidents" if South Korea and the United States did not stop allowing tourists and journalists to visit the Demilitarized Zone that divides the peninsula.

North Korean state media warned of a possible loss of lives because of the tours, which it says violate the armistice that ended combat in the Korean War in 1953.  The tours have gone on for decades.