Armed police have rushed to a major London hospital during an "ongoing incident".
The Met Police said it had arrested a man at Central Middlesex Hospital, in Acton, on Wednesday afternoon, but could not immediately give more details.
Armed police were among those responding, officers confirmed.
The London Ambulance Service said it had so far treated two people at the scene and said the incident was still ongoing.
"I am at Middlesex Central hospital in the dialysis unit and we're sheltering in safe rooms," said one of those at the hospital, Amie Ferris-Rotman.
"Armed policemen are on the scene, being described as a 'major incident'".
A spokesperson for London North West University Healthcare Trust, which runs the hospital, advised patients: "There's an ongoing incident at Central Middlesex Hospital.
"Please follow any instructions given to you by the police."
More follows.
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