The Department of Marine and Wildlife Resources in American Samoa is advising the public not to swim or fish in Pago Pago Harbour until the cause for the source of the water's strange colouring is discovered.
The department says investigations will need to be carried out to determine the current cause of excess phosphates in the harbour, which is likely to not be algal blooms as in the past.
A biologist, Alice Lawrence, says a fish was seen swimming erratically upside down in the inner harbour in August and was later found dead.
She says tissue samples have been sent to the Center for Disease Control in Hawai'i for analysis.
"We have had a lot of reports of actual schools of fish just swimming upside down, strangely, like floating so like not looking very healthy at all. And recently over the last few days we have had more reports - I think it is getting worse. Also we have had reports from some of the kids that swim in the marina, they have stopped swimming in the marina because they started to get like boils on their skin and itchy problems."