The blaze at the Rathbones bakery at the Wakefield 41 Industrial Estate was reported at 4:15pm.
The fire service reported about 80% of the 7,990m2 single storey factory was on fire. The fire was not treated as suspicious.
Inspector Paul Maxfield of Wakefield District Neighbourhood Patrol said: “Due to the size of the fire, a large number of fire appliances were deployed which necessitated road closures around the scene.
About 50 firefighters with 15 fire engines battled the blaze through the night.
“The fire is not being treated as suspicious and there were no serious injuries but a small number of members of staff were treated for smoke inhalation.
“We are doing everything we can to minimise disruption to neighbouring businesses and the surrounding community.”
Morrisons told FoodManufacture.co.uk: “There was a fire at our Rathbones bakery in Wakefield. All colleagues were evacuated quickly and safely.”
Debris from the blaze was found landing about half-a-mile away from the site, according to some reports on Twitter.
One twitter user said: “Everybody was watching for miles. People were screaming ‘Morrisons is on fire’. There was flying burnt bread in people’s gardens.”
‘Flying burnt bread’
The bakery was sold to Morrisons in 2005, after the previous owner bakery went into administration due to tough trading conditions and a fire at its Carlisle factory in February of the same year.
The Rathbones blaze is the second food industry fire in the past months, following a lightning strike that ignited a huge methane gas fireball at a food waste management site in Oxfordshire.
The fire at Agrivert in Benson, Oxfordshire, started when lightning ignited gas stored in a waste digester and caused £25,000 of damage.
Fire crews were called to the fire at Agrivert at about 5:19pm following a lightning strike at the facility. The blaze destroyed the factory’s roof.