A torpedo probably caused the explosion that ripped a South Korea warship in two near the border with North Korea, the South Korean defense minister said, though he wouldn’t say North Korea had fired it. Experts examined the wreckage and found that a close-range, external underwater explosion, which caused a “bubble jet effect”—when an explosion causes a rapidly expanding bubble, which releases a destructive water column. Forty sailors died in the March 26 incident, and six more are presumed dead. The defense minister would not speculate about who fired the torpedo, though in the wake of the ship’s sinking he had said North Korea was a likely culprit. That nation has denied any involvement. The two countries, still technically at war, have clashed in the same spot three times since 1999.