Natural gas safety?

I recently had a friend that lost his wife, possessions, home, and cars due to a natural gas explosion in their home. I understand they thought they had a leak, but had someone come out to identify the source, but couldn't find the leak. The blast started a fiery inferno which destroyed everything, even melting cars, computer, and safe. The blast was so severe that it rocked the community, and blew windows and doors out in the farmyard. The inferno was noted 20 miles away-large columns of smoke. Fortunately my friend was far enough away from the house working on farm equipment that he didn't get hurt. This is a true story, and probably The Des Moines Register had an article on this tragedy-believe it was April or May of this year. They traced the gas leak coming underground from a cracked gas line outside the basement wall by the footings and followed the drain tile into the basement drain. These are well respected farmers(the best) and try very hard to keep things in good repair.