Australian authorities declared almost 60 kilometres of beaches a disaster zone on Friday, two days after tonnes of oil spilled from a cyclone-hit cargo ship.

A nature conservation officer carries an oil-covered pelican from the beach on Moreton Island near Brisbane on Friday. (Tertius Pickard/Associated Press)

A Hong-Kong registered cargo ship reportedly lost tonnes of oil after its hull was breached amid harsh conditions caused by stormy weather on Wednesday. An investigation is underway to determine the cause of the spill.

National parks at Moreton and Bribie islands north of Brisbane, the capital of the state of Queensland, were among the worst hit areas. Stretches of normally white sandy beaches on the Sunshine Coast, north of the state capital on the mainland, were also blackened by the oily sludge.

The state's premier, Anna Bligh, said the spill "may well be the worst environmental disaster we have seen in southeast Queensland."

Bulldozers and other heavy machinery began moving to affected areas to scrape up the blackened sand after the beaches were closed to public access.

Wildlife authorities said the only animal victims so far were a handful of birds that had been soaked in oil, but warned things could get worse as long as the slick remained.

On Thursday, the Queensland government said it expected the cleanup could take up to seven days. Bligh has come under fire for moving too slowly to mitigate the damage caused by the spill, but defended her government's cleanup efforts.

"You don't walk in on Day 1 and take all of the sand off the beach, only to have more oil overnight coming in on the tide, necessitating more sand be taken off on the second and the third day," she said Friday.

"These are sensitive environments and you need to be systematic and clear it with almost military precision."

Shipowner may have to foot bill

State officials have threatened the ship owners with a multimillion dollar lawsuit.

Britain's Swire Shipping Ltd., the Hong Kong-registered ship's owner, said containers aboard the ship had slipped from the deck as it rocked in cyclone-stirred waters, ripping a hole in a fuel tank and spilling the equivalent of approximately 42.5 tonnes of heavy fuel oil into the sea.

Later, the company said a diver's inspection of the hull had led it to conclude the amount of spilled oil was "significantly more" than that, but did not give a revised figure.

Queensland state officials accused the company of initially misleading the government about the size of the spill. Bligh said the company had earlier told the government the spill was much smaller, leading officials to predict there would be little environmental damage.

"We will be pursuing these ship's owners for full compensation for the cost of this cleanup," Bligh said. Swire "should stand on notice that they will get a very large compensation claim from the Queensland government," she said.

Under Australian law, the ship's owners face fines of up to $2 million ($1.7 million Cdn) and could be liable for up to $250 million ($210 million Cdn) more in penalties for causing environmental damage.

In a statement, Swire said it "regrets the extent of the environmental pollution caused by spills of heavy fuel oil from the ship and the company is offering assistance with the clean up."

The company and its insurers were in discussion with the government about cleanup costs, it said.

The potential for long-term environmental damage was not clear. The affected area is far to the south of the Great Barrier Reef, which is not under threat.

With files from the Associated Press and the Australian Broadcasting Corporation