A group of school children made a remarkable discovery while playing inside a cave on an old Kalbarri property.

The children had been visiting the Murchison House Station with their parents when the group made a rest stop.

The machine gun is believed to be dated from 1917. Credit: Courtney Lou

It is understood the children had been climbing over the nearby rock formations when they stumbled inside a small cave on the Murchison property.

Murchison House Station detailed the children's discovery on their Facebook page.