Fire Crews at Famous London Hospital

Witnesses report a loud explosion as the fire spread, which is said to have come from a gas canister in the cardiac wing of the hospital, although the London Fire Brigade could not confirm this.

All patients and visitors to the hospital are said to have escaped the fire unharmed.

Six fire engines and 35 firefighters were at the scene after being notified of the fire at 8.35am. 

There is no smoke visible at the scene.

Chief executive Dr Jane Collins said "a number" of day and in-patients had been cleared from the building.

Great Ormond Street Hospital treats over 150,000 children each year for rare and complex conditions.

The hospital is based in the heart of London, near Russell Square tube station.