More than 100 firefighters were at the scene at the peak of the incident/Stephen Huntley/BBC
Twenty firefighters were taken to hospital after a blaze ripped through an industrial unit and spread to a fertiliser store, triggering a major explosion.
The fire service declared a major incident on Friday, as more than 100 firefighters tackled the flames at Highlands Farm, near the village of Rettendon, Essex.
Three fire engines and two fire service cars were destroyed in the blaze.
Speaking at a media conference on Saturday, Rick Hylton, Essex's chief fire officer, praised the "remarkable professionalism, courage and commitment" of the fire crews.
He said the incident was "one of the most challenging and complex incidents Essex County Fire and Rescue Service has responded to in recent years".
Of the firefighters taken to hospital, four had minor injuries. Sixteen were checked as a precaution for issues such as hearing loss after the explosion.
All of them had been discharged from hospital, Hylton said.
The fire service was called at about 16:50 BST on Friday to reports of a fire involving industrial units and surrounding land at the farm, on Southend Road between East Hanningfield and Rettendon.
Firefighters were confronted by a large and "quickly developing" blaze, Hylton said.
At 17:46 a unit housing fertiliser exploded.
Witnesses told the BBC it sounded "like a bomb" and compared it to a "sonic boom".
Others described hot debris falling from the sky.
On Saturday, about 25 firefighters remained at the scene dampening down. An investigation into the cause of the fire is under way.
Hylton said the fire service was also working on recovery operations for businesses affected.
