A major incident was declared as 100 firefighters battled a huge blaze south of Chelmsford.

A huge explosion triggered by a fire spreading to a store of fertiliser tore through an industrial unit in Essex on Friday, with more than 100 firefighters sent to tackle a massive fire and a "major incident" declared. Footage which captured the moment of the explosion showed a ball of flames erupting into the air and people fleeing, while witnesses told BBC News the sound was "like a bomb" and as loud as a "sonic boom". A number of buildings and vehicles on farmland were gutted by the fire, which was expected to keep burning into Saturday. People living near the fire - which happened close to the village of Rettendon, south of Chelmsford - were urged to keep their windows closed as smoke spread. In an update on Friday evening, Dave Bond of Essex County Fire and Rescue Service said: "While on the scene, fertiliser inside one of the units exploded and residents across the county have reported hearing and feeling it. "This is why we declared a major incident and I want to reassure our residents that there is no wider risk to the public at this time." He said "everybody at the scene is safe" but that residents have been evacuated. East of England Ambulance Service said its hazardous area response team and the police were also in attendance.