Thanks for the reply sadoun.

There is only one factory, the area is houses and plastic polytunnel producing tomatoe and cucumber, the storm drain leads to it. I use the mill for my own olives !

No have not done any tests , there is no need it really, smells of olive residue the same as in some pits here, nothing else could produce this.

But would like to know if it is harmful before I take it further.
Cheers
ColD