The Old Bailey has been evacuated following reports of a 'major explosion' nearby.
Emergency services attended the scene in central London where smoke has been spotted in an adjacent building.
There have been reports of buildings nearby suffering from power cuts.
LBC News reports that officials at the Old Bailey are responding to an emergency, after reports of a power cut caused by a fire next door.
Emergency services are expected to remain at the scene throughout the day
GB News
London Fire Brigade said in a statement: "Firefighters are currently responding to reports of smoke coming from a building on Warwick Lane."
Nearby eyewitnesses said they saw "black acrid smoke" coming from rear of Central Criminal Court, Old Bailey.
They added: "Lights flickered inside before it was evacuated - firefighter says fire in section of building where electrical substation sits."
The incident is currently not being treated as terror related. It has been reported that 1,500 people were evacuated from the building.
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The Old Bailey had to be evacuated this morning (file pic)PAA worker in an adjacent building told BBC News that he heard rumbling before black smoke appeared.
Recorder of London, Judge Mark Lucraft said he heard loud bang and saw smoke, reports The Times' David Brown.
He added that it was "too early to say" when cases will resume at the Old Bailey.
There have been unconfirmed reports that the fire was caused by works taking place at the back of the building.
A spokesperson from the London Fire Brigade said: "Four fire engines and around 25 firefighters are responding to an incident involving an electrical substation on Warwick Lane, near the rear of the Old Bailey.
"Traffic in the area is likely to be impacted as we respond. The Brigade was first called about the incident at 10.44am. Firefighters from Dowgate, Soho and Dockhead Fire Station are at the scene.
"The cause of the fire is not yet known."