The fire that tore through Baldock industrial estate last week was started by a wood burning water boiler, the Comet can reveal.

Firefighters from Hertfordshire Fire & Rescue Service raced to the scene in London Road on Tuesday, July 11, after being called at 6.15pm, and remained at the fire as of 10.30pm, having declared a "major incident".

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More than 40 units were affected by the blaze, with Hertfordshire County Council confirming earlier this week that the fire started "accidentally", but could not confirm where it originated.

However it has now been established where the fire started, with a spokesman confirming to the Comet: "Hertfordshire Fire and Rescue Service, having completed an investigation into last week’s major fire at Baldock industrial estate, has determined that the fire started accidentally.

"The fire began in the flue of a wood burning water boiler, first spreading to the roof and then throughout the remainder of the building affecting a large number of business units."

READ MORE: WATCH: Fire rips through Baldock industrial estate