GOMA, Congo—Congo’s Mount Nyiragongo unleashed lava that destroyed more than 500 homes on the outskirts of Goma, but witnesses said Sunday that the city of 2 million had been mostly spared after the volcano erupted at night and sent thousands fleeing in panic. Authorities said at least five people had died in a road crash while trying to leave Goma, but cautioned it was too early to give a death toll in the hardest hit communities. Residents said there was little warning before the dark sky turned a fiery red, leading to fears that the eruption could cause the same kind of devastation as the last time in 2002 when hundreds died. The U.N. peacekeeping mission had said late Saturday that it didn’t appear the lava was flowing toward Goma based on reconnaissance flights, but untold thousands still set off fearing the worst. Some boarded boats onto Lake Kivu while …