MELBOURN- - Mining giants Rio Tinto, BHP Group and Fortescue Metals said their Australian operations had suffered some impact after two cyclones hit the country over the weekend, with clean up starting on Monday in the wake of the storms.

Cyclone Veronica has been weakening after battering Australia's northwest, while further east, Cyclone Trevor was downgraded to a low pressure system on Sunday.

Businesses affected included those in the iron ore export hubs of the Pilbara region, as well as Rio Tinto's bauxite operations in Weipa to the east.

Rio said in a statement on Monday that some of its iron ore mining and rail operations had been impacted by the weather, but that there had been no reports of injuries to employees.

"Normal operations will resume once safe to do so," it said.

The key iron ore ports of Port Hedland, Dampier and Ashburton remained closed, operator Pilbara Ports said on Monday.

Rio is the main exporter at Dampier, while BHP and Fortescue ship from Port Hedland.

BHP said that it had deployed staff to assess the overall effect of the weather at its sites, with any impact on production to be reported in its next operational review due in April.

"Initial inspections show water damage to some buildings at Nelson Point (in Port Hedland) and we are currently working through this situation," a spokeswoman said in a statement emailed to Reuters.

Fortescue said it expected a 1.5-milllion to 2 million tonnes of iron ore shipments to be delayed due to Veronica, assuming that Port Hedland reopened in the next day. "Tropical Cyclone Veronica is expected to weaken further as it tracks westwards close to the Pilbara coast today. Conditions have eased at Port Hedland," Australia's weather bureau said on Monday.

Meanwhile, global miner Glencore said its McArthur River zinc operations and nearby loading facility in northern Australia were returning to normal following Cyclone Trevor.

"All our workforce have remained safe and our infrastructure and water management systems are in excellent condition," the firm said in an emailed statement.

A state of emergency had been declared late last week in the northeast, with large-scale evacuations taking place.

Ahead of the cyclone, Rio suspended its Weipa bauxite mining operations at the northeastern tip of the country.