"While molasses is not harmful to the public directly, the substance is polluting the water, causing fish to die and could lead to an increase in predator species," the state health department said in a statement Wednesday.
"The nutrient-rich liquid could also cause unusual growth in marine algae, stimulate an increase in harmful bacteria and trigger other environmental impacts."
Marine life began dying Monday, when a ship loading 1,600 tons of molasses destined for the U.S. West Coast suffered a pipeline leak that dumped 233,000 gallons of the viscous material into the waters of the harbor.
"This is the worst environmental damage to sea life that I have come across, and it's fair to say that this is a biggie, if not the biggest, that we've had to confront in the state of Hawaii," health department Deputy Director Gary Gill told KHON-TV, Honolulu, Thursday.
The molasses in the harbor will eventually dissipate naturally, dissolving in water and being flushed out by the currents, but estimating how long that will take is difficult, experts said.
The health department, in a statement, said it would "monitor the [molasses] plume and judge how long it will take to flush out to sea."
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