Feds blame gas company for deadly Mass. explosions
Federal investigators say deadly natural gas explosions in northern Massachusetts last month stemmed from faulty work orders.
The investigators say Columbia Gas failed to instruct the workers to deactivate pressure sensors when taking an old cast-iron gas main out of service. When those sensors detected a drop in gas pressure, the system increased the pressure. Within minutes, houses across Lawrence, Andover and North Andover began to explode.