Authorities suspect that someone threw an object in the way of the train, causing the crash, police department spokesman Adam Navarro said. Police detained a 30-year-old man suspected of being homeless and suffering from mental health problems in connection with the derailment, officials said.
There are significant delays in Manhattan, Ms Feinberg said. Service on the A trains is suspended in both directions south of 14th Street and there is no northbound service along Eighth Avenue from Canal Street to 59th Street-Columbus Circle.
Service is limited in upscale Manhattan and the Bronx. All northbound A, C, D, E and F trains are rerouted.
Ashley Southall contributed reporting.