In situations like those, if I'm not sure but there are probable answers, I usually say: we're not sure yet, it could be X or Y, but we need ... time to know fo

In situations like those, if I'm not sure but there are probable answers, I usually say: we're not sure yet, it could be X or Y, but we need ... time to know for sure. The other people are usually smart enough to know if they need a more precise answer or not. If I have completely no idea, then I just say so.