Firefighters are still working to bring the fire under control in the building which measures 30 metres by 40 metres.
Firefighting operations were interrupted earlier this morning because of multiple explosions from inside the premises.
The suburb of Mitchell remains evacuated due to concerns over the possibility of toxins in the smoke from the fire. Police are operating road blocks on all entrances to Mitchell. People should avoid the area until further notice.
Evacuation centres has been established at Canberra Stadium and Dickson College.
An EMERGENCY ALERT telephone advice has been issued for residents within a 10 kilometre radius to remain indoors until further notice.
People are urged not to ring 000 unless for a life threatening emergencies. All telephone inquiries should be made to Canberra Connect on 13 22 81.
Firefighters have been forced to retreat back from the fire following multiple explosions and are now reassessing firefighting options.
ACT Fire Brigade has issued an EMERGENCY ALERT about the presence of a potentially toxic smoke plume to the suburb of Mitchell between Flemington Road and Gungahlin Drive and the Barton Highway and Wells Station Drive.
The ACT Fire Brigade has confirmed the fire is burning within an amount of mineral oil within the building.
Firefighters are now re-commencing firefighting operations using water and foam.
The ACT Fire Brigade has now ordered the evacuation of the whole suburb of Mitchell including a number of campers at Exhibition Park.
There is still a localised smoke plume but there is no threat to nearby residential suburbs of Harrison and Franklin.
Residents are advised to remain indoors.
The building is located in the newer industrial estate of Mitchell off Hoskins Street.
Firefighters have been forced to move a few hundred metres back from the premises while working with the business operator to identify what substances are inside the building.
The business, Energy Service International (ESI), works with materials including oil from electricity transformers.
The fire has produced a thick smoke plume in the immediate area.