An eyewitness has told talkRADIO about the moment the explosive device detonated at Parsons Green station.
The authorities have said the explosion is being treated as a terrorist incident.
Pictures on social media show a sort of white cannister with wires extending out of it as a potential cause of the blast.
Mark had been sat on the train at the moment the device was detonated.
He told our reporter Tania Snuggs, who is at the scene, what happened: "I was at the back of the train, on the last carriage. It was stationary at Parsons Green, the doors were open.
"There was what I thought was a small explosion, I initially thought it was an electrical explosion at first.
"It caused a quite bit of panic, people exited the train onto the platform where it was apparent people were injured."
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