The full scale of the environmental disaster on the Queensland coast was becoming clear last night as a shipping company admitted that its earlier estimates of the size of the oil spill were "substantially" wrong.

Oil blackens the sand along Kawana Beach on Queensland's Sunshine Coast as environmental experts fear the damage from an oil spill will be worse than first thought. (Photo: Getty Images) An oil slick was blackening beaches along the Sunshine Coast, Bribie Island and Moreton Island.

Even as authorities focused on the damage to these areas - now declared disaster zones - more oil spilt into the Brisbane River. This 500-metre-long slick was contained quickly.

As experts warned that the environmental damage could worsen, the State Government said it would take at least two weeks to clean up.

On the beach at Bribie Island yesterday, council workers were raking the sand, turning up the globules of oil.

The stricken cargo vessel Pacific Adventurer was still leaking oil from a breach in its hull late yesterday as it lay moored in Brisbane's port, a casualty of rough seas it encountered on a voyage to Indonesia in the early hours of Wednesday.

"I think it's fair to say the Government and authorities were not informed accurately of the size of the spill," said Allan Sutherland, the Mayor of Moreton Bay, where part of the clean-up was taking place.

He said the ship's owners, Swire Shipping, "were hoping mother nature would take its course. It didn't."

Last night, Swire Shipping, admitted the damage was worse than it had announced earlier.

It said a diver's examination of the Pacific Adventurer's hull showed the damage was worse than initially believed.

"It is likely that substantially more oil has spilled than the earlier estimate of 42.5 cubic metres (42.5 tonnes)," it said.

Authorities say up to 100 tonnes of oil may have leaked.

The Government yesterday doubled the estimated time it would take to clean up the beaches, saying it would take at least two weeks. The clean-up, being undertaken by hundreds of government staff with earthmoving machinery and rakes, will cost $100,000 a day.

Maritime Safety Queensland warned that the effects of the spill would probably get worse before they got better.

The chief executive of the Australian Maritime Safety Authority, Graham Peachey, said it had detained the Pacific Adventurer "and it's not going anywhere until we release it".

Swire Shipping was co-operating with investigators, who are examining the ship's actions since before it left Newcastle on Tuesday carrying more than 800 tonnes of ammonium nitrate, an explosive used in mining. About 600 tonnes of ammonium nitrate, sealed in shipping containers, was lost overboard during the storm.

The investigation will include an examination of reports that the ship's master was reluctant to leave port and sail into the aftermath of tropical cyclone Hamish.

Queensland Premier Anna Bligh said those responsible for the oil leak would feel the full force of the law, saying the incident "may well be the worst environmental disaster Queensland has ever seen".

"We will also be pursuing them for compensation as this is going to be a very big clean-up cost and I want those ship owners to be paying for it," she said.

The Queensland Opposition, wildlife carers and environmental groups have accused the Government of a slow and inadequate response.

Liberal National Party leader Lawrence Springborg said Labor had failed to have an appropriate emergency plan in place.

He said the LNP had initially told that "everything was under control", only to find out later that "we have a disaster on our hands".

Deputy Premier Paul Lucas said the response had been adequate, but the Government had not been told of the full extent of the spill.

"When someonehas lied to you about the level of leakage of oil, then it is a very difficult situation to be in," he said.

The World Wildlife Foundation said the spill would affect every level of the marine food chain.

Foundation spokesman Martin Taylorsaid everything from fish and crabs to waterbirds, dugongs and dolphins, would feel the effects.

"It's a mass poisoning event, effectively," he said,

"so unless people get out there and clean it up as fast as possible, that poison will kill marine life for years."

So far only about 13 animals were known to be affected by the oil, but the Environmental Protection Agency was expecting the number to rise.

With AAP