Blast investigated by health and safety officials
An investigation into an explosion at an industrial complex has been launched by the Health and Safety Executive (HSE).
The blast, triggered by flames spreading to a fertiliser store, led to 20 firefighters being taken to hospital on Friday.
They had been called to Highlands Farm, near Rettendon in Essex, where the fire had been ripping through business units, at 16:50 BST.
Inspectors said they would examine the scene, speak to witnesses and work with Essex County Fire & Rescue Service during their inquiries.
More than 100 firefighters tackled the blaze, which was likened to a "sonic boom" due to the noise it sent across the region.
Of those taken to hospital, four had minor injuries and the others were treated for issues including hearing loss.
Stephen Huntley/BBCThe HSE said Essex Police would also be involved in its investigation.
"The focus of HSE's investigation is to establish whether there has been any breach of workplace health and safety regulations," a spokesperson said.
It would also determine a formal cause of the fire, they added.
They continued: "Our inspectors continue to work in close co-operation with Essex County Fire & Rescue Service as its firefighters work to bring the site to a safe resolution."
People affected by the incident have told the BBC of their shock at seeing the explosion, described by one as "like a bomb" going off.
Tony Maher said his family-run metalworks business lost £1m worth of equipment when its premises was destroyed.
A helpline has been set up by Chelmsford City Council for those in need of support.
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