It is now quite evident that the storm and the conditions which followed were not of natural origin.

There were no sounds which were not of natural origin.

This appears man made but is thought to be of natural origin.

They were quickly determined to be of natural origin, however.

The next step is to find more about these trace vapours, including whether they are of natural or human origin.

However, as a product from natural origin it is a mixture of many different compounds.

But you're not returning to your place of natural origin, anyway.

No theory has yet been able to explain this storm, which was clearly not of natural origin.

Creatures native to the world generally have the natural origin.

The word "animal" shows that music is of a natural origin.