A week of official mourning has been declared as thousands of Poles light candles to mourn the death of their president and 96 others in a plane crash. A somber vigil, stretching into the early hours of Sunday, was observed in central Warsaw's Pilsudski Square to mourn the president and the other people killed when their plane crashed on Saturday while trying to land in thick fog in western Russia. The 97 people aboard the 26-year-old plane were heading to Katyn, the site of a 1940 massacre of Polish prisoners of war whose bodies were dumped in unmarked graves by Soviet secret police. In addition to President Lech Kaczynski and his wife, the dead included the army chief of staff, the head of the National Security Office, the national bank president, the deputy foreign minister, the deputy parliament speaker, the civil rights commissioner, and other members of parliament. War veterans and surviving family members of Poles killed by the Soviets in Katyn were also killed in the plane crash. Crowds laid red and white roses in front of the 200-year-old presidential palace near Warsaw's old town, while flags flew at half mast.