Thousands of dead fish have washed up on the shores of Rio's Guanabara Bay, not far from where events are being held at this year's Olympic Games.
The incident is the latest involving water quality in the bay, where sailing, open water swimming, and triathlon will take place.
The Brazilian government's State Environmental Institute has found rubbish in the water and on the beach, as well as a considerable number of dead fish all from the same species of sardine.
Officials claim these fish, because of their low commercial value, are often thrown overboard by trawlers.
Other than floating garbage the officials saw no visual abnormalities in the water.They took samples and will report back in five days.