The blaze broke out at a robotic warehouse in Andover, Hants, around 24 hours ago, but around 200 firefighters have struggled to bring the fire under control.
Hampshire Fire and Rescue Service (HFRS) said: “The blaze that is sweeping through the Ocado warehouse in Andover has been declared a major incident.
“About 200 firefighters have been tackling the fire which broke out at 2.44am on February 5.
“Four firefighters have been treated for slight smoke inhalation.
“Part of the roof has no collapsed and the fire in the complex robot-run distribution centre is still ongoing.”