South32, which owns Worsley Alumina in the region, has pledged $A50,000 to assist with relief and rebuilding efforts for communities affected by the south-west bushfires.

"We are a long-standing member of the South West and Peel communities and we understand first-hand how this tragic event will impact families and businesses in the region," chief operating officer, Australia Ricus Grimbeek said.

"Our hearts go out to those who have lost homes, livestock or been impacted by these catastrophic fires."

Alcoa is still working to restore normal operations at its Wagerup refinery near Waroona, but access to the site remains restricted.

"There are currently no active fires impacting the plant, however Alcoa fire crews continue to monitor burnt out areas," the company said.

"There have been no injuries to employees or contractors reported as a result of the fire."

The Willowdale bauxite mine remains suspended and Alcoa is working on establishing safe employee access to allow operations to restart.

Alcoa owns 80 houses in Yarloop, the worst-affected town where two people died, but the company is yet to gain access to assess the damage.

"Our sympathies are with all those who have suffered losses in the fire," the company said.

"We will do everything we can to assist employees and the local communities as they recover from this tragic event in the coming weeks and months."