Nine people including seven children were injured, some believed critically, on Thursday when a car collided with a primary school building in southwest London.
Police said they were not treating the incident at the private Study Prep girls' school in Wimbledon, as terror-related.
Local member of parliament Stephen Hammond told the BBC he understood that a number of the casualties were "being treated as critical", describing the crash as "extraordinarily distressing and tragic".
Aerial footage of the scene -- not far from where the Wimbledon tennis tournament was taking place -- showed a Land Rover car stopped at an angle against the wall of the modern school building.
The vehicle was in a grassed area near what appeared to be coloured play mats and a table.
The police, ambulance and fire service were all called to the scene on Camp Road, near Wimbledon Common, after the incident just before 10:00 am (0900 GMT).
Witnesses and reporters on the spot said the road outside the school was a narrow one on which it would normally have been difficult to build up any speed.
The Study Prep school takes girls from aged four to 11. It is split into several sites, with the youngest pupils taught on Camp Road, near the Royal Wimbledon Golf Club.
Thursday was the last day of term for children aged four to eight, according to the school's website.
"Several people are being treated at the scene. We are not treating this incident as terror-related," the Met added in a statement.
"An investigation is under way to understand the full circumstances of what has taken place," it added.
The driver stopped at the scene and no arrests were made, it added.
Health Minister Steve Barclay said in a tweet he was being kept up to date with “the distressing incident”.
"My thoughts are with those sadly injured and everyone who has been affected," he added.
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