A man was taken to hospital after dozens of guests were evacuated from a five-star hotel following a chemical spillage.
Emergency services were called to the Milestone hotel in Kensington Court, close Kensington Palace, in central London, on Thursday.
Early indications suggest the leak of the cleaning agent was accidental, London Fire Brigade (LFB) said.
A man was treated at the scene and then taken to hospital, London Ambulance Service said.
Emergency response crews checked the area for any raised chemical levels but found nothing, LFB added.
Some 50 hotel guests were evacuated along with another 30 people from an adjacent flat block as a precaution.
Road closures remain in place, the Metropolitan Police said.