Early Saturday, a locomotive pulling a 72-car freight train full of crude oil from North Dakota was parked for the night 11 km west of Lac-Megantic, Quebec, the engineer checking into a nearby hotel. Sometime shortly after, the unattended train began to roll away, toward Lac-Megantic -- investigators are still looking for the cause. The crude oil cars, rolling downhill, broke free of the locomotives and picked up speed, derailing at a curve in the center of Lac-Megantic, a lakeside town of about 6,000 people. Six massive explosions followed, sending up huge fireballs and setting dozens of buildings ablaze. Thousands were evacuated, and so far, five deaths have been confirmed. Authorities worry the toll will climb much higher, as more than 40 residents are still listed as missing.