RIO DE JANEIRO (Reuters) - Indigenous people from nine villages in Brazil's Yanomami territory were found to be contaminated by mercury, with those living closer to illegal gold mining sites presenting higher levels of contamination, a study released on Thursday found.

The study by Brazil's state-run Fiocruz institute collected hair samples from about 287 Indigenous people in October 2022. They all tested positive for contamination by mercury, with around 11% of the samples presenting high levels of the heavy metal, which is used by wildcat miners in Brazil to separate gold from ore and earth.

The Yanomami, estimated to number about 28,000, live in Brazil's largest Indigenous reservation, in the northern states of Roraima and Amazonas. They face a humanitarian crisis due to the invasion of their lands by illegal miners that has caused malnutrition and deaths.

"This scenario of vulnerability exponentially increases the risk of illness in children living in the region," specially in those under five years-old, Paulo Basta, who coordinated the study, said in a statement.

Indigenous people with higher levels of mercury presented cognitive deficits and more often presented nerve damage on their bodies' extremities, according to the study.

Over 80% of those who participated in the study told researchers they had had malaria at some point.

Over 25% of children under 11 in the study were anemic, and almost half had acute malnutrition. Around 80% were shorter than expected for their age, suggesting chronic malnutrition as well, the study found.

All of the 47 samples of fish collected by Fiocruz researchers also tested positive for mercury contamination.

"Our children are being born sick. Women are sick, our old people are sick! Our people are dying because of mining," Dario Kopenawa, head of the Yanomami's Hutukara Association said in a press statement that accompanied the study.

(Reporting by Fabio Teixeira; Editing by Sandra Maler)