Assistant Commissioner Pat Goulbourne said: “Firefighters were called to reports of people feeling unwell at a bank on Golders Green Road in NW11.
“A number of people were experiencing a range of symptoms, which could indicate exposure to a chemical or other substance.
“Four fire engines and several specialist appliances were sent to the scene. Crews carried out a thorough search of the area using detection, identification and monitoring equipment and have now confirmed there are no elevated levels of hazardous materials present.
“Firefighters remain on scene to provide support and assistance to the local community."
The Brigade was called at 1541. Fire crews from Euston, Bexley, West Hampstead and Kentish Town fire stations attended the scene. The incident was under control by 1727.