Firefighters were called to reports of smoke on a train at Tower Hill underground station. The train was inbound from east London to Ealing Broadway.
The London Fire Brigade said that a mobile phone charger was the "cause". After the blast took place the passengers ran in panic to save their lives.
Initial reports are suggesting that battery charger exploded, police are not treating this as terror related.
The station was closed following the incident.
The British Transport Police confirmed just after 1pm that the incident was thought to be caused by a "mobile phone charger overheating".
A spokesman for British Transport Police told Metro.co.uk: "We are now on the scene alongside the London Fire Brigade, after responding to a fire alert on the District Line".
Transport for London said there was disruption on the circle and district lines while the matter is dealt with. However, officials say the fire was "nothing serious".
On September 16, a home-made bomb on a packed rush-hour commuter train in London engulfed a carriage in flames and injured 29 people on Friday, but apparently failed to fully explode, in Britain's fifth major terrorism incident this year.