Firefighters evacuated the building on Cabot Square after reports of the “smell of chemicals” in the building. The brigade said a mixture of chemicals caused high levels of fumes and vapour.

Firefighters were called at 9.08am and a man was treated at the scene by the ambulance service. The incident was ongoing at midday.

Station Commander Dave Hill, 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.”

Two fire engines from Millwall and Poplar fire stations and two fire rescue units from Bethnal Green and Euston fire stations were at the scene.