Explosion in New York City subway

New York City Police Department officers stand guard near the New York Port Authority Bus Terminal on Dec. 11, 2017.

Police block a street by Port Authority Bus Terminal near New York’s Times Square following an explosion on Dec. 11, 2017. Police say the explosion happened in an underground passageway under 42nd Street between Seventh and Eighth Avenues.

New York Gov. Andrew Cuomo speaks to members of the media after a pipe bomb strapped to a man went off in a New York City subway near Times Square on Dec. 11, 2017, in New York. Mayor Bill de Blasio stands fourth from left.

Police secure Eighth Avenue outside the Port Authority Bus Terminal following an explosion near New York’s Times Square on Dec. 11, 2017. Police said a man with a pipe bomb strapped to him set off the crude device in an underground passageway under 42nd Street between Seventh and Eighth Avenues.

Police stand guard in front of the Port Authority Bus Terminal near New York’s Times Square following an explosion on Dec. 11, 2017. Police say the explosion happened in an underground passageway under 42nd Street between 7th and 8th Avenues.

A police officer stands guard in front of Port Authority Bus Terminal as law enforcement respond to a report of an explosion near Times Square on Dec. 11, 2017, in New York.

People walk past Port Authority Bus Terminal as police respond to a report of an explosion near Times Square on Dec. 11, 2017, in New York.

Police block off a sidewalk while responding to a report of an explosion near Times Square on Dec. 11, 2017, in New York.

A crowd moves past police responding to a report of an explosion near Times Square on Dec. 11, 2017, in New York.

Police respond to a report of an explosion near Times Square on Dec. 11, 2017, in New York.