Two chemical tanks have exploded during a blaze at a design manufacturing plant in Essex.
Six fire crews were called to the Sil-Die factory in Fullbridge, Maldon, at 1245 GMT.
Two phosphorus tanks have exploded and crews have been hampered by a number of potentially explosive chemicals.
The fire service said the two-storey property has been "totally destroyed" and a heavy plume of smoke can be seen over the town.
An Essex Fire and Rescue Service spokesman said: "First one tank exploded and then that made the second tank explode.
"There was a huge bang and the explosion created a bright white flash with pieces of phosphorus flying out everywhere.
"Crews are battling hard at this incident but the chemicals involved are creating problems. Parts of the building have already collapsed.
"A specialist chemical officer has been ordered to the scene as the basement is thought to contain magnesium developer and acetone fixer."
Roads in the area have been closed. An emergency refuge has been set up by the local authority to provide shelter for those unable to return to their homes.
At 1645 GMT Assistant Divisional Officer Nigel Dilley said the fire was coming under control but that crews expected to remain on the scene for some time.
He said: "The factory itself has been totally destroyed - the roof has collapsed, some of the walls are still standing but there was nothing crews could do to save it.
"The early call from the owner and the information he gave regarding the chemicals and their potential reaction to first crews at the scene averted a much more serious incident.
"We have a fire investigation officer involved in the incident although at this stage we are not treating it as deliberate."
Sil-die is a foiling and embossing manufacturer which produces artwork and design services.