SAN JUAN, Puerto Rico: A massive explosion ripped the side off a six-story building in San Juan Thursday morning, killing at least 19 and injuring 82. Investigators believe a natural gas leak may be responsible, but are looking into other possible causes. The blast, believed to have originated in a shoe store, carved a 50-foot-wide hole out of the side of the building which is located in a residential and shopping district. "There were just parts of bodies lying in the street, torsos, bones, cars blasted against the building," Police Chief Pedro Toledo said. Owners of the shoe store said they had reported a gas leak to the San Juan Gas Company several days ago. Utility company workers were continuing repairs this morning when the blast occurred. Up to 15 people are believed missing, possibly trapped under the piles of mangled debris. The explosion was so powerful that shards of glass and concrete burst through the windows of a nearby elementary school, but none of the students were hurt.