Emergency services are responding to reports of an explosion near Times Square in New York.
The New York Police Department said the explosion at 42nd Street and 8th Avenue in Manhattan was of "unknown origin".
In a statement on Twitter it said that three subway lines were being evacuated, adding: "Info is preliminary, more when available."
The response is centered in the area of the Port Authority bus terminal.
There were no immediate reports of injuries.
ABC News, quoting police sources, reported that the explosion was caused by a "possible pipe bomb" detonated below ground and said a suspect was in custody.