South Korea suspects the DPRK intentionally flooded a river at their shared border last weekend. Rescuers have now recovered the bodies of a boy and two others engulfed by the surge of water.
The Imjin river starts in the DPRK and ends in the South to the northwest of Seoul.
Last Sunday, the DPRK unleashed an estimated 40 million tons of water from a new dam without warning.
The surge swept away six people who were camping on the riverbank at the time.
On Wednesday, all six bodies had been recovered.
Pyongyang said in a letter on Monday, that they released the dam water because of too much water in the river. It also said it would issue alerts in the future to prevent a recurrence.
Hyun In-Taek, S. Korea Unification Minister, said, "DPRK itself admitted that it let the water out, but we definitely see that there is some intention. However, we are currently analyzing what the purpose could be."
Analysts said the move could set back inter-Korean relations, which have improved in recent weeks after 18 months of tensions.
Seoul has demanded more explanation and an apology from Pyongyang.
(CCTV September 10, 2009)