An industrial unit at Highlands Farm, near Rettendon, Essex, caught fire on 24 July, with the blaze then spreading to a nearby fertiliser store.
The fire caused a serious explosion and required more than 100 firefighters from Essex County Fire & Rescue Service to bring the incident under control.
The ferocity of the blaze led to the destruction of three fire engines and two fire service cars, while 20 firefighters who responded to the incident were taken to hospital.
Several businesses operating from units at the industrial complex have seen their stock and premises largely destroyed as a result.
Four firefighters suffered minor injuries, while 16 were assessed for hearing loss due to the sonic boom caused by the explosion.
HSE has revealed that it is now working alongside Essex County Fire & Rescue Service and Essex Police to establish the facts surrounding the incident.
Through its investigation, HSE will seek to determine whether there has been any breach of workplace health and safety regulations at Highlands Farm, including factors that contributed to the fire and subsequent explosion, as well as other aspects relating to the site and emergency response.
