Emergency services rushed to Parson's Green on Friday (September 15) morning responding to reports that a bag "exploded" on board a packed District Line train causing passengers to "suffer facial burns."
A security alert was raised at 8.20am following reports of an explosion, triggering panic among commuters during rush hour.
The Wimbledon District Line service was suspended and the Metropolitan Police and emergency services attended the incident.
A spokesman for Met Police said: "We are aware of an incident at Parsons Green tube station. Officers are in attendance. More info ASAP."
Large crowd gathers outside Parsons Green station as passengers fled from the incident.
Media technology consultant Richard Aylmer-Hall, 53, was sitting on the District Line train bound for central London when panic unfolded.
He said he saw several people injured, having apparently been trampled as they tried to escape.
He said: "I was on my way up from Wimbledon towards Paddington and suddenly there was panic, lots of people shouting, screaming, lots of screaming.
"There was a woman on the platform who said she had seen a bag, a flash and a bang, so obviously something had gone off."
He added: "I saw crying women, there was lots of shouting and screaming, there was a bit of a crush on the stairs going down to the streets.
"Some people got pushed over and trampled on, I saw two women being treated by ambulance crews.
"Since then, every emergency vehicle in London has gone past me, fire engines, ambulances, every type of police vehicle."
Pictures on social media show a white bucket inside a plastic bag in flames on board the tube.
Natasha Wills, of London Ambulance Service said: "We were called at 8.20am to reports of an incident at Parsons Green underground station.
"We have sent multiple resources to the scene including single responders in cars, ambulance crews, incident response officers and our hazardous area response team, with the first of our medics arriving in under five minutes.
"Our initial priority is to assess the level and nature of injuries. More information will follow when we have it."
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