St. Petersburg Metro Explosion

Blast victims lie near a subway train hit by a explosion at the Tekhnologichesky Institut subway station in St.Petersburg, Russia, April 3, 2017.

A subway train hit by a explosion stays at the Tekhnologichesky Institut subway station in St.Petersburg, Russia, April 3, 2017.

People carry a subway blast victim into an ambulance after explosion at Tekhnologichesky Institut subway station in St.Petersburg, Russia, April 3, 2017.

People carry a subway blast victim into an ambulance after explosion at Tekhnologichesky Institut subway station in St. Petersburg, Russia, April 3, 2017.

A helicopter flies over the fire trucks after an explosion at Tekhnologichesky Institut subway station in St.Petersburg, Russia, April 3, 2017.

In this image taken from video footage, emergency services work outside Sennaya Square metro station in St Petersburg, Russia, April 3, 2017.