HUALIEN, Taiwan—A Taiwan express train with almost 500 aboard derailed in a tunnel on Friday after hitting a truck that had slid down a bank onto the track, killing at least 50 passengers and injuring 146 in the island’s worst rail disaster in seven decades. Images from the scene showed some carriages ripped apart by the impact, with others crumpled, hindering rescuers in their efforts to reach passengers. By mid-afternoon no one was still trapped, though the fire department said it had found body parts, meaning the number of those killed, who included the driver, was likely to rise. “People just fell all over each other, on top of one another,” a woman who survived the crash told domestic television. “It was terrifying. There were whole families there.” Taiwan’s government said there were 496 people on the train, including 120 without seats. Many were tourists and people heading home at …