Loft insulation in veg. plot

I have been digging a new veg. plot and have found what looks like loft insulation in buried in the ground, I have dug out most of it but there is quite a bit still in there. Any ideas on whether I should continue to use the ground as a veg. plot or should I move to cleaner bit of the garden.

 

Glass fibre insulation shouldn't cause a problem. Some of the horticultural fleeces and weed barriers are made of glass fibres and glass is an inert substance. I'd continue to use the ground and just dig out the stuff as and when you come across it.
Mineral wool is used as a growing medium mainly in hydroponics as well as insulation. So I'd guess that you should be safe enough.