A total of 22 people - including children - were injured in the explosion, with a lot of them suffering from "flash burns and are being treated in hospital, mostly for burn injuries".
- Some people suffered burns while others injured in a stampede to escape, witnesses said.
The cause of the blast was an "improvised device" that failed to fully explode, police said.
"The officers from the Metropolitan Police Service and the British Transport Police are in attendance along with the London Fire Brigade and the London Ambulance Service".
"People started to run but we were lucky to be stopping at Parsons Green as the door started to open".More news: Oracle Corporation (ORCL) - Jefferies Maintains Rating And Raises Price Target
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The Metropolitan Police said "a number of people" had been injured and advised people to avoid the area.
Photos taken inside the train show a white plastic bucket inside a foil-lined shopping bag.
Transit officials increased security Friday at Bay Area BART stations in the wake of a terrorist bombing in London that left 22 people injured.
The police statement said that it was too early to confirm the cause of the fire and the station has been cordoned off.
May also said the British terror threat level would stay at "severe" rather than raising it to "critical", although this would be kept under review.
U.S President, Donald Trump condemned the attack, calling the attackers as "loser terrorist".