Molasses spill off Hawaii prompts warning after killing fish

Health officials warned swimmers, surfers and snorkellers in Hawaii to stay out of the waters near Honolulu after a leak of 1,400 tonnes of molasses killed hundreds of fish, potentially attracting sharks.

So many fish had died by Thursday that the Hawaii Department of Health tripled cleanup crews to three boats, which removed hundreds of fish and were to remove thousands more in the coming weeks, said department spokeswoman Janice Okubo.

A brown plume of sweet, sticky liquid was spotted seeping into Honolulu Harbour and Keehi Lagoon on Monday after a ship hauling molasses to the US' west coast pulled out to sea.

By Tuesday, a leak was discovered in a molasses pipeline used to load the molasses onto ships operated by Matson Navigation Co, an international ocean transport company, the health department said.

Roger Smith, a dive shop owner who went underwater on Wednesday to survey the damage, said it was unlike anything he had seen in 37 years of diving, with brown-tinted water and a layer of molasses coating the sea floor.

"Everything that was underwater suffocated," Smith said. "Everything climbed out of its hole and the whole bottom was covered with fish, crabs, lobsters, worms, sea fans - anything that was down there was dead."