The scale of the environmental disaster unfolding in the ocean off Brisbane is becoming clear, with an ABC reporter on Moreton Island saying oil spills have turned the sand black "as far as the eye can see".

Around 20 tonnes of fuel oil leaked into the sea yesterday after a cargo ship was holed as it lost part of its load in rough seas whipped up by Cyclone Hamish.

Huge oil slicks are drenching beaches at the northern end of Moreton Island and Queensland Sustainability Minister Andrew McNamara says more oil is expected to come ashore.

ABC reporter James Kelly is on Moreton Island's ocean beaches this afternoon.

"There's oil on the beaches as far as the eye can see," he said."It's black, it's several millimetres thick, and there's an almost overwhelming stench."

The authorities are today inspecting the damage but say the clean up could take months.

They say it is likely bulldozers will be brought in to scoop up the toxic deposit from the beaches and the shallows.

Mr McNamara says the spill will also reach Bribie Island.

"The modelling that we have indicates that more oil will come ashore and unfortunately more birds will be caught up in that," he said.

Volunteers are trying to wash the oil off newborn turtles and eggs and pelicans.

Smaller amounts of oil have also washed ashore at Marcoola Beach further north on the Sunshine Coast.

Moreton Island is a near-pristine sand island off Brisbane which is popular with fishermen, campers and beachgoers.

Greens leader Bob Brown says the Federal Government should be providing all possible help to Queensland authorities to clean up the oil spill.

Senator Brown says Commonwealth authorities need to explain how the ship was allowed to travel into areas which were badly affected by a tropical cyclone.

"We need to know that there are huge resources being mobilised to offset the potential environmental and human consequences of this spill, and to make sure it doesn't happen again," he said.

"It should not have happened on this occasion."

'Clean-up could take years'

Channel 7 pilot Greg Rogers says the slick will take months, if not years, to clean up.

"The worst of it is still within the 10-kilometre radius of the cape but it's still quite evident on the beach," he said.

"The pristine white sands of Moreton Island are very black in places today."

He says the scene is reminiscent of the 1978 Amoco Cadiz oil spill in France.

"It's just one continuous black beach from Cape Moreton down to ... Blue [Lagoon] and there is evidence of less contamination further south," he said.

Mr Rogers says the high tides have pushed the contamination right up into the sand dunes.

"All the rocks are covered in oil - God knows how many millions of crustaceans have died as a result," he said.

Government defends response

The Queensland Government has defended the time it has taken to respond to the 20-tonne oil spill.

Mr McNamara says the potentially dangerous chemicals and severe weather conditions hampered efforts to inspect the spill yesterday.

"First off, the boat had to be made safe," he said.

"There was 25 kilos of ammonium nitrate that entered the fuel tank which contained a very significant amount of fuel oil - that has to be resolved before you can have people in and around the vessel.

"Similarly there was 2,000 kilos of ammonium nitrate mixed with oil on the ship's deck."

Queensland Transport Minister John Mickel says the Pacific Adventurer will dock at the Port of Brisbane this morning, with investigations underway into how the incident happened.

"The Australian Transport Safety Bureau, the Australian Maritime Safety Authority are working with Maritime Safety Queensland to conduct a full investigation of what happened with this incident," he said.

Wildlife dying

Queensland Environmental Protection Agency (EPA) spokesman Clive Cook says it has started treating wildlife injured by the spill.

He says choppy seas are spreading the oil slick north-west from Moreton Bay.

"We've had one confirmed report of a sea bird with oil on it and two others unconfirmed, so we are prepared for the contingency of treating oiled wildlife," he said.

"We have a number of staff trained up in oiled wildlife response.

"They're spread up and down the coast and we're starting to back up the initial crews."

Earlier surf lifesaver Dave McLaine said there was a lot of oil washed up at Marcoola.

"It's quite heavy in some spots - I've just been down there for a walk myself and have come back and it's caked all over over my thongs and all over my feet," he said.

"I've just spent about 15 minutes in the shower trying to get it all off."

Resident Robyn Cameron also says her feet have been covered in black oil at Marcoola beach.

"It's up to my ankles," she said. "I first thought it was just the foam from the rough conditions and then I realised, 'oh my goodness, this is oil', so I've been out with the citrus cleaner to scrub it off with a brush."