Counter-terrorism sources say, they are treating the London Parsons Green Tube Train explosion as terrorism.
The incidence happened this morning in South West London after fire was reported on the train.
Here is what witnesses are saying…
Passenger Chris Wildish told BBC Radio 5 live he saw a bucket in a supermarket bag with “low-level flames coming out of it” by the door of the rear carriage.
One witness, called Luke, told 5 live there was “a sort of loud explosion”.
“It happened just as we were pulling up to the Tube station so everyone just sort of piled out of the Tube and there was a distinct smell of burning,” he said.
“I certainly saw some burning injuries,” he said, but added that “everyone behaved in the right manner as such, everyone got off as quickly as they can and you know supported everyone”.
Emma, who was at Parsons Green station, said: “We were running down the stairs like… it felt like for our lives.
“I went down the stairs and after a while people were just piling on top of each other, because people were falling over trying to run so quickly.
“There were two ladies underneath me and a little boy to my right, his head had been smacked into the concrete.”
BBC London presenter Riz Lateef, who was at Parsons Green on her way in to work, said: “There was panic as people rushed from the train, hearing what appeared to be an explosion.
“People were left with cuts and grazes from trying to flee the scene. There was lots of panic.”
BBC News presenter Sophie Raworth says she saw a woman on a stretcher with burns to her face and legs.
Alex Littlefield, 24, a City worker, said: “I was walking around the corner to the Parsons Green Tube station and I saw the raised platform with everyone running and looking upset.
“I saw police officers, fire brigade… masses of people and armed police. There were lots of very, very distressed people. We’ve been pushed right back now.”