A Polish government commission on Monday said a 2010 plane crash in western Russia that killed then-President Lech Kaczynski and his wife was likely caused by a bomb on board. The announcement came on the seventh anniversary of the crash, which led to a rift between Moscow and Warsaw for years afterward. Polish authorities have expressed suspicions that Russia was behind the catastrophe, though Moscow has denied those claims. The plane, which was transporting top Polish officials to a ceremony in Smolensk to mark the execution of thousands of Polish officers in 1940, went down as pilots were attempting to land in thick fog. On Monday, however, a new Polish commission investigating the crash cast doubt on the idea that it was an accident. “Much indicates that on April 10, 2010, an explosion took place on board of the government Tupolev plane,” a statement from the commission said. “As a result of the conducted experiments, we can say that the most likely cause of the explosion was a thermobaric charge initiating a strong shockwave,” the statement said. All 96 people on board were likely killed before the plane hit the ground, investigators said. The commission, set up by Defense Minister Antoni Macierewicz, also reiterated earlier claims that Russian air-traffic controllers intentionally directed the plane onto the wrong descent path. Russia has denied the allegations and said it is conducting its own investigation into the crash with the wreckage, which it has so far refused to return to Poland.