An archaeologist doing an assessment of Toorale Station, a former cotton and grazing property west of Bourke, discovered the remains, which were exposed by erosion.

Jackie Roberts, a spokeswoman for the Department of Environment and Climate Change, said the burials were at different locations in an area bounded by the Darling and Warrego rivers.

Subject to confirmation, the bones were deemed to be ancient.

"Their exact age has not been determined and is unlikely to be determined as we don't plan on disturbing them any more than is absolutely necessary for their protection," she said.

The land was originally occupied by the Baakantji people, who lived between present-day Bourke and Wilcannia. The National Parks and Wildlife Service has notified Aboriginal elders and initial steps have been taken to protect the sites.

Ms Roberts said the locations will be treated sensitively for future management of the park.

"Aboriginal remains are uncovered several times a year. This is not surprising considering the length of time Aboriginal people have existed in Australia. The remains are often uncovered during excavation works, although that was definitely not the case in this situation."

She said remains are always managed in consultation with Aboriginal communities.

The 91,000-hectare Toorale Station was bought by the NSW and federal governments for $24 million last September, with five other properties along the Darling River system to allow enough water to remain in the rivers to keep them healthy.