Hundreds of people were evacuated from the Canary Wharf area following a “chemical incident” at a health club.
London Fire Brigade (LFB) Service said crew were called to reports of a smell of chemicals at an address in Cabot Square.
A mix of chemicals had caused high levels of fumes and vapour in the building, the brigade said. One man and one woman were treated at the scene by London Ambulance Service crews.
Pictures from the scene showed at least four fire engines were sent to deal with the incident. A "hazard zone do not cross" cordon was put in place as firefighters carry out checks.
Dave Hill, station commander who is at the scene, said: “Crews have carried out a sweep of the building and found elevated readings.
“Firefighters have ventilated the building and are monitoring the levels of fumes.
“We have evacuated around 900 people from the building as a precaution.”
The Brigade was called to the scene just after 9am. The incident was declared over and people were allowed to return to the buildings at around 12.30pm.
Two fire engines from Millwall and Poplar fire stations and two fire rescue units from Bethnal Green and Euston fire stations were sent to the scene.
LFB dealt with a similar incident late last month following a chlorine leak at the Aquatics Centre on Queen Elizabeth Olympic Park in Stratford.
Due to a chemical reaction, a high quantity of chlorine gas was released, LFB said at the time.
A number of patients were treated at the scene. Around 200 people were evacuated from the centre.
Fire crews used fans to ventilate the premises.
“Once low levels were reported on our detection equipment we handed the centre back to the building owners,” LFB said.
