Armed police are among officers who have been called to a reported stabbing at a hospital.
One man has been arrested, the Metropolitan Police said.
Some reports on social media suggested that patients at Central Middlesex Hospital in north west London had to shelter in safe rooms, but this has not been officially confirmed.
In a statement on Twitter, London Ambulance Service said it was at the scene with paramedics and an air ambulance and hazardous environment team have also been dispatched.
LAS said: “We’ve sent a number of resources to the scene, including an incident response officer, an advanced paramedic, an ambulance crew, a medic in a fast response car, and@LAS_HART.
“We also dispatched @LDNairamb. The incident is ongoing and we are working with our emergency services partners.”
