Emergency authorities have reduced the size of an exclusion zone around a huge chemical fire in Canberra as the threat of a toxic smoke plume diminishes.
But as a precaution, all schools in Canberra's north have been closed for the day.
ACT Emergency Services Agency chief Mark Crosweller said early fears about a potentially toxic plum had "abated immensely".
As a result the initial 10-kilometre exclusion zone around the factory fire in Mitchell has been reduced to 300 metres.
Mr Crosweller warned there could be further explosions inside the factory as firefighters battled to contain the blaze.
Atmospheric tests of the smoke plume have found almost undetectable levels of phosgene which is contained in the by-product of the substance being burned, PCB.
Phosgene is known to cause irritation to skin and eyes, sore throat, nausea, headaches and dizziness, vomiting, chest pain and difficulty breathing.
Testing will continue throughout the day but the ACT Fire Brigade believes the risk to residents is low.
Technical assistance has been sought from fire and safety authorities in NSW.
Mitchell residents and campers at the nearby local showground were evacuated shortly after an explosion at the factory before midnight on Thursday.
They were taken to an evacuation centre at Dickson.
Firefighters have returned to the factory site after they were forced to withdraw from the scene because of the fire's intensity.
The firefighting operation had a long way to go, Mr Crosweller said, adding it was a complex operation.
Smoke from the fire has drifted to the neighbouring NSW centres of Queanbeyan and Bungendore, about 40 kilometres from Canberra.
But warm weather has helped dissipate the smoke.
