Their job is to keep the public safe. People digging too close to gas pipelines cause most accidents. Even a hand-held shovel can damage some gas lines. Backhoes and bulldozers can damage any pipeline. This is why laws require gas companies to mark the location of their lines, to support programs like diggers hotline , and to watch for signs of future building or digging on private land near their lines.
Natural gas is a safe fuel.
But when used improperly it can be very dangerous. A major break in a pipeline, where a large volume of gas escapes at once, is usually caused by careless digging. When a pipe breaks, the escaping gas is dangerous if it builds up in a closed space like a basement. If conditions are right, it can explode. If you smell gas, leave the building at once.