Firefighters are expected to remain at the scene throughout the day
More than 60 firefighters tackled a fire which severely damaged a complex of industrial units in Bedfordshire.
Bedfordshire and Luton Fire Service was called to Clophill Road, in Maulden, shortly before 0400 GMT.
A fire service spokeswoman said some of the buildings contained propane cylinders and one had a tank containing caustic soda.
People living downwind of the fire were advised to keep their windows and doors closed until it was contained.
Dave Fothergill, the fire service's area commander, said: "The smoke plume was high so we did not anticipate any real concerns for the public.
"But just in case, we advised those living in the Millbrook direction to keep their windows shut."
An investigation into the cause of the blaze has started.
The fire began in a pine-stripping workshop at the back of a block of small commercial units. It spread via the roof into the other buildings.
Crews from Bedford, Ampthill, Kempston, Stopsley, Toddington, Woburn, Biggleswade and Potton were involved in fighting the blaze.