A coworker brings you a bag of oatmeal in which he has found black specks. what is the most likely cause of those specks

There are multiple possible answers. One is that it's mouse droppings since mice like to eat it. Another is that it's bugs and this is dangerous since they can leave larva there. The third is that they are remaining residue traces from other types of oats that were ground together and in this case it is not that dangerous.