A defense ministry official later said that the unidentified object the vessel had fired at on Friday night near the western sea border that divides the two Koreas may well have been a flock of birds. Initial fears that North Korea might be to blame caused ripples on Wall Street, where share prices dipped partly on geopolitical concerns, and the South Korean won dropped against the dollar. “It is premature to discuss the cause of this sinking,” presidential Blue House spokeswoman Kim Eun-hye told Reuters early on Saturday. “It is not clear whether North Korea was involved.” The Joint Chiefs of Staff also said it could not conclude that the reclusive North was behind the attack. Yonhap news agency quoted a presidential official as saying satellite pictures and other information showed no sign of the North Korean military in the area at the time of the sinking. The defense ministry said 58 of the 104 on board had been rescued and Yonhap quoted navy officials as saying several had died. “An unidentified reason caused a hole in the ship, which led to its sinking. Currently 58 have been rescued out of the total 104 on board. Rescue efforts are under way,” the ministry said.