What caused historians to think that the eruption of Mount Vesuvius in 79 CE was not the only reason why the residents of Pompeii died? Sources from that period explain that residents fell ill and died from the volcanic mud. Newly discovered accounts explained that most residents died instantly from fires after the eruption. Sources from that period show that residents did not take the threat of eruption seriously and stayed in the city. Recent scientific advances proved that polluted water from the volcano most likely killed any residents who drank it.