SÃO PAULO, Brazil – Brazil's federal police are investigating allegations by an indigenous group that farmers poisoned a creek they rely on.

The investigation into the alleged poisoning started Tuesday, reported the Associated Press. A spokesman for the federal police in Mato Grosso do Sul state said the Guarani-Kaiowás told him the water in question runs through sacred land.

According to Primeira Edição, the indigenous community insisted the alleged crime was "a deliberate action by the landowners."

Members of the Guarani-Kaiowá tribe, including children, were bathing in the Ypo'i creek last Wednesday when a white foam started coming out of the water, reported BOL Notícias. Pictures and videos were taken by those present and were sent to the Ponta Porã Federal Police Attorney General. It took two days to clear the foam, according to the tribe.

Some of those who saw the foam followed it to its source, which they said was a farm with two drums in view, BOL Notícias also noted.

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"We don't know [what was in them]. We went to take pictures, but we were greeted with a bullet," one Guarani-Kaiowá said. "They started shooting into the sky and we started running."

The Guarani-Kaiowá are entangled in a land dispute with farmers who claim the 2.5 acre plot the tribe occupies belongs to them, according to the AP. Last month, a judge allowed the 170 indigenous people to stay on the land. The Indigenous Missionary Council said three men from the tribe have been killed since 2009. One man bore signs of torture and was dumped in the creek.