Three people are dead and 64 injured after following a massive explosion in New York's Harlem on Wednesday morning. The explosion and collapse of two buildings at 1644-1646 Park Avenue were apparently caused by a gas leak, which was reported 15 minutes prior to the explosion. Crews arrived after the disaster. Nine occupants are still unaccounted for. “We are expending every effort to locate each and every loved one," said Mayor Bill de Blasio. "We don’t want to speculate who might be in the building and their situation until we have the ability to get closer."