Two fires that destroyed 19 homes in Stourbridge were started accidentally in fields where farming machinery was in use, according to West Midlands Fire Service.
Investigators established agricultural equipment was being used in the vicinity of fields immediately before the fires were first reported. The service would not confirm the type of machinery.
The first fire started in a field near Racecourse Lane at about 13:27 BST on 13 August, while a second began shortly afterwards in a field near Quarry Park Road.
The day after the fires the government sent out an emergency alert to millions of people across England and Wales, warning them against "any activity that could start a fire".
Justifying why the alert had been sent, Prime Minister Andy Burham said: "I was in Stourbridge today and saw first-hand the devastating impact these fires have had on people's homes and lives."
The Stourbridge blaze was one of the most significant incidents West Midlands Fire Service had ever dealt with, Chief Fire Officer Simon Tuhill said. A major incident had been called as the wildfire spread across more than 500 acres and destroyed the 19 homes.
Tuhill said on Wednesday so many people had been affected he wanted to confirm both fires were not started deliberately. They were accidental, he said.
"While investigations continue into the full circumstances of what happened, we wanted to share this latest update as soon as possible," he continued.
"I hope it will go some way towards helping people understand what happened on that exceptionally hot and challenging day."
Some residents were taken to Stourbridge Town Hall after the evacuation and given support by volunteers.
The town also saw a great community effort as residents pulled together to help those in need and also to praise the farmers who had helped put the fires out.
The Bishop of Dudley, the Right Reverend Martin Gorick, was among those who were forced to evacuate.
"We saw houses going up in smoke in front of our eyes. Absolutely tragic," he said at the time.
Robin and Loxie Williams saw their four-bedroom house destroyed. They had lived there for 26 years and said they had been forced to watch their neighbourhood going up in flames on TV.
"I know that many are still struggling to comprehend the scale of damage and personal loss," Tuhill added.
"I'm also acutely aware that this information will not bring those back homes, livelihoods or cherished memories.
He added he was proud of the fire service response, plus that of colleagues in the police, ambulance and local farming community.
"The response to this incident showed the very best of Stourbridge and the wider West Midlands."
Several other fires were reported in the West Midlands on the same day as a total of 54 patients were treated by paramedics and 19 were taken to hospital.
Other incidents saw about a dozen homes lost in Birmingham, four in Stoke-on-Trent, three in Pershore, Worcestershire and three in Willenhall, near Wolverhampton.
The causes of most are still under investigation, although it was confirmed a barbecue started the one in Stoke on Trent.
