Crews were called out to the blaze at the Rönnskärsverken smelting plant at 2.25am on Tuesday, but at 2.45pm the inferno was still raging.

There is little risk that the fire will spread, because the plant is located near the water in the harbour, officials told the TT news agency. But a public safety announcement was issued earlier in the day of toxic fumes, urging those in the area to go indoors and close windows, doors and vents.

As of 2.45pm, the announcement had been withdrawn, but officials have warned that the situation could change if winds shift and start to blow smoke over the city.

Two ambulances were dispatched to the site in the morning and two people received oxygen treatment, reports regional newspaper Norran. But they did not need hospital care and there were no immediate injuries reported.

Around 20 firefighting units were battling the blaze on Tuesday morning, which was under control by 2.45pm.

Two helicopters from the Civil Contingencies Agency were also dispatched from Östersund to be at the ready in case the flames spread and cause a forest fire.

The risk of wildfires is in general currently high or very high in Skellefteå and all across Sweden, after weeks of warm weather have left the woods tinder-dry.

Rönnskärsverken is located in Skelleftehamn, a small town in Skellefteå municipality.