Advice please re: return to field 3 months after rabbit bait?

One of my boy's favourite places to go for a run had a rabbit bait drop on 8/5/2011 it was Magnesium Phosphide. He's far too big to get down a rabbit hole being a 35kg labx and is only really interested in the chase. But I just want to be safe. I can't find any information anywhere on when it might be ok to go back.
Does anyone have any ideas?

Thanks

Helen & Zac

I would ask your local vet?

Found these statements relating to it.

Properly exposed material is not a hazardous waste.

When this product is used out-of-doors in a site frequented by people, other than an athletic field or park, the applicator shall post a sign at the application site containing the signal word DANGER, skull and crossbones, the name and EPA registration number of the fumigant, and a 24-hour emergency response number may be removed 2 days after the final treatment.

Seems it is reasonably safe after just a few days if used properly

Doh,
how stupid do I feel! of course I should just ring the vet! will be doing so on Monday!!

Alf, thanks for your research, but I wonder if that is information based for humans? The scavenger I have is likely to munch on any bones he comes across (including rotting flesh that may be attached) & would that be harmful? Easy to tell him no if I'm with him but if he's off down the field?!

will let you guys know what the vet says!

Helen