Sydney - The Australian Navy was called in Monday to look for 31 containers that fell overboard when the Pacific Adventurer fell victim to a cyclonic storm off Brisbane last week.

As well as losing half its cargo of ammonium nitrate, the Hong Kong-owned ship spilled oil over 60 kilometres of beaches in Wednesday's accident.

Authorities have impounded the 180-metre vessel in Brisbane harbour and begun legal proceedings against the captain and the ship's owner, Swire Shipping Ltd.

The Queensland state government is demanding compensation for cleaning up the oil spill and for any loss of tourism earnings through hotel room cancellations.

The lost boxes contain 620 tons of ammonium nitrate, an ingredient used in the production of fertilizer. Planes have been up to look for the lost containers but none has been spotted.

The chemical is unlikely to prove a threat to marine life but the lost containers pose a risk to shipping, officials said.

Queensland Seafood Industry Association president Neil Green said containers bobbing in the ocean were worrying trawler captains.

"We're horrified," he said. "Looking at the location of where these containers went over, it's smack bang in the middle of our trawl grounds." (dpa)