The Natural History Museum in a tweet confirmed the "serious" incident and said they are working with the police to get the situation in control.
Of the 11 injured, nine have been taken to hospital, the London Ambulance Service said.
Witnesses described a rush to leave the scene, nearby shops were evacuated and the sprawling museum, a favorite site for families with children, closed down early.
The paramedics are on the spot and have been giving medical treatment to the injured people.
Crowds in the busy tourist spot in South Kensington, which is also home to the Victoria & Albert Museum and the Science Museum, fled screaming in panic, an AFP reporter said. They added a man had been detained.
Police said a number of people were injured and one person was detained at the scene.
Authorities determined that the incident was a "road-traffic collision" after four hours of investigation. She said she was told by police injuries sustained were minor.
It is not clear that the incident which took place today had any terrorism connection, according to PTI.
"Details are emerging and I have spoken with and am in close contact with Assistant Met Commissioner Mark Rowley and our other emergency services".
Officers have detained a man at the scene while officers investigate what has happened and any motive behind the incident.
She says "he looked really proud of himself. he was laughing".
A Downing Street spokesperson said British Prime Minister Theresa May is "being kept up to date on events".
Inmediaciones de NaturalHistory Museum #Londres Hombre reducido en el suelo antes de que lleguepolicÃa, no sabemos q pasa.
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