Officials believe the capsule was lost while it was been moved from a mine site north of Newman and a depot in Perth for repairs on Jan.
The capsule contains a small quantity of radioactive Cesium-137, which could cause serious illness and skin burns if touched, the BBC reported.
When the package was opened for inspection on Wednesday, a gauge was broken and the capsule was missing.
So if you have contact or have it close to you, you could either end up with skin damage, including skin burns, over a period of time.
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