LONDON - An explosion on a Tube train in south-west London is being treated as terrorism, Scotland Yard has said. Passengers were injured following the blast at 08:20 BST at Parsons Green station on the District Line.
Pictures show a white bucket on fire inside a supermarket bag, but do not appear to show extensive damage to the inside of the carriage. Eighteen people had been taken hospital, the London Ambulance Service said in a statement.
The Metropolitan Police said it was too early to confirm the cause of the fire and the station has been cordoned off.
Prime Minister Theresa May tweeted: "My thoughts are with those injured at Parsons Green and emergency services who are responding bravely to this terrorist incident."
Mayor of London Sadiq Khan has appealed for calm, saying the city "will never be intimidated or defeated by terrorism".
Witnesses have described seeing at least one passenger with facial injuries. Others have spoken of "panic" as alarmed passengers left the train at Parsons Green station.
Passenger Peter Crowley said he was sat in the carriage, travelling eastbound from Wimbledon, when the explosion happened. He said his head was burned by a "really hot intense fireball above my head" and added: "There were people a lot worse than me."
Passenger Chris Wildish told BBC, he saw a bucket in a supermarket bag with "low-level flames coming out of it" by the door of the rear carriage.
At Parsons Green, a helicopter flies overhead as confused and concerned members of the community wait on the street for more news. Police cordon has been put up around Parsons Green station, with every side street blocked off by blue and white tape.
Police vehicles are still rushing down the west London road, with sirens blazing as they pass supermarkets, furniture stores and music shops. And bit by bit, commuters who were stuck on the trains behind are being allowed to exit.
Justine Daniels had just arrived from South Africa, laden with suitcases, when her Tube train came to a stop.
"We were on there for over an hour before they let us out through the emergency exit and we walked along the tracks," she says.
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. 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," he said.
Emma Stevie (27) who was on the train when the explosion happened, and said she was caught in a "human stampede" and crush on the station steps as people rushed away from the train.
"I wedged myself in next to a railing, I put myself in the foetal position. There was a pregnant woman underneath me, and I was trying really hard not to crush her. I saw a poor little boy with a smashed-in head and other injuries. It was horrible. The injuries from the stampede seemed the worst. I'm outside now, there are women crying and people sitting on the floor," she said.