The explosion that rocked New York City's Chelsea neighborhood, injuring 29, is not believed to be an act of terrorism, although it could be "an intentional act," New York City Mayor Bill de Blasio announced in a press conference late Saturday night. There is no known link between the blast and credible threats against the city, de Blasio clarified, nor to the Saturday morning pipe bomb blast in New Jersey. New York City Police Commissioner James O'Neill also ruled out natural gas as a cause and said "it appears the explosion happened on the street." He also confirmed that there is an ongoing investigation into a "second device" on 27th Street between Sixth and Seventh Avenues.