A cargo ship that spilled 31 containers of ammonium nitrate into Queensland's Moreton Bay in the wake of Cyclone Hamish has also leaked heavy fuel oil.
The Hong Kong-flagged Pacific Adventurer cargo ship was travelling from Newcastle to Brisbane in rough seas near Point Lookout at Stradbroke Island in southeast Queensland when the container spill happened about 3am (AEST) on Wednesday.
Maritime Safety Queensland general manager Captain John Watkinson said that in a case of Murphy's Law, a falling container damaged the ship's hull where the heavy fuel oil was stored.
"One of the containers as it went over the side, with the movement of the ship, has pierced the hull," he told ABC Radio.
"So the ship has lost a little heavy fuel oil. No one has been harmed as far as we're aware.
"We've spoken to the ship's captain and he was a bit anxious with his condition out there, with the sea, which has been whipped up by Cyclone Hamish. It's a pretty nasty situation."
Capt Watkinson could not say whether all the spilt containers would be retrieved.
"The ship's master indicated that he thought the containers had sunk. The other (possibility) is that they're still floating around out there. We've got a plane or chopper going out there soon."
An emergency services spokeswoman said three tonnes of ammonium nitrate spilt on the ship's deck.
Australian Maritime Safety Authority (AMSA) spokeswoman Tracey Jiggins said the containers, which contain granular ammonium nitrate, were sealed so it was unlikely they would leak.
She said AMSA's environmental protection response team also believed the ammonium nitrate was of low toxicity and wouldn't damage marine life.
But Dr James Smith, a water quality expert at the Queensland University of Technology, said that if the contents of the containers leaked, the spill could create algal blooms, which would choke life on the Moreton Bay marine bed.
"The risk of the impact (of the ammonium nitrate) is nitrification, which is algae blooms," Dr Smith told AAP.
"Ammonium nitrate is very soluble, so once it gets wet, it will dissolve fairly quickly."
Although authorities said the containers remained sealed, Dr Smith said they would eventually corrode.
"They won't stay intact forever," he said.
Moreton Bay already had some problems of coastal algae bloom, he said.
The company in charge of the ship, Swire Shipping, said there had also been a small spillage of fuel oil from a damaged tank, but the crew had transferred all oil from the damaged tank to other tanks and no further oil was spilling.
"The vessel is currently proceeding to the Brisbane inner anchorage with a pilot on board and is in no danger," the company said in a statement.
"Swire Shipping... is co-ordinating with authorities to minimise any environmental damage and any hazard to other shipping."
A severe weather warning remains in place between the northern tip of Fraser Island and Coolangatta due to Hamish.
The Bureau of Meteorology said a large high pressure system over the western Tasman Sea in combination with Hamish was producing strong to gale force winds and large waves along the southeast Queensland coast.
