London Subway Explosion

An injured woman is led away after an incident at Parsons Green underground station in London, Britain, September 15, 2017.

Deputy Chief Constable Adrian Hanstock of the British Transport Police makes a statement to the media after an incident at Parsons Green underground station in London, Britain, Sept. 15, 2017.

A police forensic officer stands beside the train, at left, where an incident happened, that police say they are investigating as a terrorist attack, at Parsons Green subway station in London, Friday, Sept. 15, 2017.

This is an image made from video showing burning items in underground train at the scene of an explosion in London Friday, Sept. 15, 2017.

In this image made from video, a woman with blankets wrapped around her is being escorted by emergency services near the scene of an explosion in London Friday, Sept. 15, 2017.

In this aerial image made from video, a police officer works at the Parsons Green Underground Station after an explosion in London Friday, Sept. 15, 2017.