In Tonga, residents living near Neiafu Tahi waters on Vava'u have been warned not to eat food from the area or nearby areas.
Tonga Broadcasting says Neiafu Tahi waters turned red on Monday and after that dead marine life washed up on the shore.
The new Minister of Fisheries, Semisi Fakahau, said they're still trying to identify the cause of the problem.
He said they will then send a sample to labs overseas if local authorities cannot pinpoint the problem.
The Minister said it is important that people abstain from fishing in the area as it might be toxic for consumption.
Semisi Fakahau said there's a possibility that the problem is caused by climate change and global warming.
Neiafu is the second-largest town in Tonga and has government offices, banks, schools, a police station and a hospital.
It is also an important centre for tourism with many yachts anchoring in the Port of Refuge.