At least 33 tonnes of dead fish have been removed over the past week from the shores of a Rio lagoon where Olympic rowing and canoeing events are due to take place in 2016, officials said on Thursday.
More than 60 people have been working daily since last week to cleanup the remains from Lagoa Rodrigo de Freitas.
While Rio's environmental secretariat claimed that the deaths occurred due to a sudden change in water temperature, scientists pointed out that fish were starved of oxygen because of pollution, the BBC reported.
Water quality still remains a major concern for organisers in Guanabara Bay, where Olympic sailing events are scheduled to be held in next August.
Earlier in the week, Rio Governor Luiz Fernando Pezao had admitted that there was 'not going to be time' to finish the cleanup ahead of the Olympic games.