Traffic lights in the Trafalgar Square area are reportedly not working following an alleged electrical explosion on nearby Cranbourn Street.

An eye-witness reported police and ambulances on the scene after a flash and a cloud of smoke. Blottr has been told by someone at the scene that a worker was electrocuted.

Pictures show an air ambulance landing in Trafalgar Square.

The lack of traffic lights is causing severe delays. Police are in attendance.

Photograph courtesy of @DanHowe.