The chaotic scenes were sparked at about midday when the train, travelling at a slow speed, overshot and crashed into buffers.
Four people were taken to hospital and five others were treated at the scene.
The Govia Thameslink Railway service had travelled from Cambridge to King's Cross before the accident.
No other injuries were reported but the London Ambulance Service confirmed it sent two crews down.
One passenger tweeted that there had been a "huge bang and everyone was thrown around".
A British Transport Police spokesman said: "Our officers were called to Kings Cross station on Thursday, September 17 following a report that a train had hit the buffers at platform 11.
"The incident was reported to BTP at 12.18pm and involved the 10.55am Cambridge to King's Cross service, which was travelling into the station at a slow speed.
“London Ambulance Service Medics also attended and four passengers have been taken to hospital where they will be treated for minor injuries.
"BTP and Network Rail are working to establish the full circumstances surrounding the incident. The Rail Accident Investigation Branch (RAIB) have been informed.”
A London ambulance service spokesman said: “We were called at 12.28pm to an incident involving a train at King’s Cross station.
“We sent two ambulance crews, an incident officer and an advanced paramedic to the scene and arrived within eight minutes.
“We treated five patients at the scene for minor injuries. We took four patients to University College Hospital.”
Network Rail said in a statement that the train was involved in a "low-speed collision with the buffer stops" at around 12.18pm.
The accident happened on platform 11, which has been closed for an initial investigation into the incident.
The Rail Accident Investigation Branch has been informed.
Comments