An explosion on a London Underground train at a station in south-west London today left several commuters injured and caused panic in the area. The city's District Line has been affected at Parsons Green station and several people are believed to have been hurt as a result of a large white plastic bucket in a supermarket plastic bag exploding in one of the carriages.While the nature of the explosion is not yet known, Police bomb squads and fire crews have been rushed to the station along with ambulances.