At least two people were killed and 16 more were injured, some seriously, in the collapse of two buildings and fire, said the New York Fire Department. Authorities, still fighting the fire and searching for victims, had reached no immediate conclusion on the cause of the explosion, but Con Edison said it was working closely with the NYFD. (Related: Q&A: How Do Explosions Cause Building Collapses Like Harlem's?)

The explosion comes at a time when utility companies in many parts of the United States are grappling with a difficult problem: what to do about aging natural gas mains, many of them in difficult-to-access locations in older urban areas, which have deteriorated and are prone to leaking. The gas mains that