Ocado has said the fire started in a corner of the grid of groceries above which its robots assemble orders.
The group's shares dropped 6% as it said it would see a fall in sales growth until it can shift operations to other warehouses following the fire at its Andover site, which took more than 24 hours to get under control.
It said that due to concerns over the presence of pressurised refrigerants at the site, the police conducted a limited evacuation of the immediate area on Wednesday evening.
More than £1 billion has been wiped off the value of Ocado after a fire savaged its warehouse in Hampshire on Tuesday night.
On Friday morning, the service said about 10 firefighters remained at the warehouse on Walworth Industrial Estate but at 16:00 GMT it said the incident had "come to an end" and the site had been "handed back to the owners".
Hampshire Fire and Rescue Service (HFRS) said "four of its firefighters had been treated for slight smoke inhalation" as they battled to bring the inferno under control.
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Ocado has apologised to those affected by a major fire at its Hampshire warehouse after nearby homes were evacuated amid a blaze firefighters are still tackling.
"This is obviously a awful event and thankfully no one has been hurt, although some firefighters have been treated for smoke inhalation".
More than 300 firefighters were tackling the blaze on Wednesday afternoon, after it was declared a major incident.
Part of the roof collapsed. Ocado is working hard to minimise disruption for customers by increasing capacity at other facilities. "Thank you. Stay safe".
The online grocer's share price fell 14 per cent in just two days as it warned the blaze would hit full-year sales.
And it said it had comprehensive insurance for the property, stock and equipment on site, and for business interruption losses.
The centre had been providing about 10 percent of Ocado's United Kingdom capacity and used the robotic technology that the firm is selling to retailers around the world.