Four people are in hospital after panicked commuters stampeded out of Dalston Kingsland station amid fears of an explosion.

People reported a smell of smoke on an Overground at about 7.15am as it pulled into the station, while one person said sparks were seen.

The source is now known to be a faulty battery pack attached to a workman’s drill.

The Overground train was evacuated in what one person called “three seconds of pandemonium”.

Hackney Council initially said there were “several walking wounded”, while London Overground tweeted that there had been an electrical explosion on board. This was downgraded by London Fire Brigade, who extinguished the smoking drill by putting it in a bucket of sand, to a “small incident”.

Medics now say four people were taken to hospital with minor head, arm and leg injuries, while three others were treated at the scene.

The incident was not suspicious.

Chris Ogden, whose wife was on board, tweeted shortly after the incident: “TfL says passenger incident, passengers stampeded off the train screaming.”

Michael Richmond added: “People started smelling smoke on a train and it evacuated in about 3 seconds of pandemonium.”

Duncan Cross, deputy director of London Overground, said: “At 7.14am today there was an incident involving a faulty drill being carried to work by a customer at Dalston Kingsland.

“The train was evacuated and the emergency services attended.

“We would like to apologise to customers who were on board and to our customers whose journeys have been disrupted.”

The Overground line was suspended between Canonbury and Stratford, with delays on the rest of the route.

A London Ambulance Service spokesman said: “We treated four patients for minor injuries, including head, leg and arm injuries, and took them to a hospital in east London.

“We also checked over three patients at the scene but they did not need hospital treatment.”