JAKARTA ~ Toxic plankton has killed thousands of fish in waters off Bali, an official said.

The “red tide,” or algal bloom, has contaminated the sea in the Tabanan district, the head of the Bali Fisheries Office Ida Bagus Putu Wisnawa Manuaba said.

“The fishes’ mass death is a natural phenomenon caused by the El Nino-induced storm that moved from the Pacific Ocean to the Indonesian waters.

“The El Nino-induced storm triggered the growth of toxic planktons called red tide,” Manuaba was quoted by the official Antara news agency as saying.

He said the toxic plankton had turned the sea red and yellow.

People living near the two beaches were warned not to eat the dead fish or swim in the waters, he said.

The main tourists beaches at Kuta and Legian further south were not reported to have been affected.

Researchers collected samples of the dead fish, sea water and plankton to investigate the deaths, Antara said.

It is not clear what causes red tides. Water pollution has been blamed but the El Nino weather phenomenon, which brings about an increase in sea water temperatures, has been linked to red tides in the Pacific Ocean.