The woman, who was thought to be in her 30s, was arrested on suspicion of trespass, and is being held at a London police station, but the Met said the incident was not being treated as terror-related.
Eleven people were injured after a auto drove into pedestrians outside London's Natural History Museum, according to the Metropolitan Police.
The London ambulance service said they had mostly suffered leg and head injuries.
The London Ambulance Service said 11 people were injured, nine of whom were taken to hospital.
"The majority of those injured have now been discharged, and there are no serious injuries", police said in a statement Sunday.
One person has been detained by Scotland Yard following the incident in Exhibition Road in South Kensington.
"When we arrived there the incident had already taken place and the Police were responding".
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I have to tell you, I had an eerie feeling that night. "As you know this is an ongoing investigation", Warren said. Life is lovely organizer Justin Weniger declined NBC's request for comment, saying the investigation was ongoing.
Video footage from the scene shows police guarding a cordon at the scene.
Security is high in Britain after five terror attacks since March - four in London and one in Manchester - which have claimed 35 lives.
In footage shared on social media, police officers could be seen pinning a man on the ground in the aftermath of the incident.
The Natural History Museum, a few blocks away from Hyde Park, is popular with locals and tourists alike and the area was busy with pedestrians braving a chilly autumn day in London.
UK Prime Minister Theresa May was being updated on the incident, her office informed.
The Metropolitan Police said the man had been arrested at the scene and initially received hospital treatment.
The Natural History Museum confirmed the incident and said they were working with the Metropolitan Police.
Britons in general, and Londoners in particular, have been jumpy after a string of extremist attacks this year, including deadly attacks using vehicles to hit pedestrians on Westminster Bridge and London Bridge.