Is yeast vegan?!

Is yeast vegan?

I just read somewhere that vegan's should avoid eating yeast but I really don't unerstand why... can anyone explain it to me?

Is there something animal derived in it or is it just because yeast is considered 'living'? Does this mean probiotics should be avoided too?

I will stop eating yeast if I know an animal has suffered for it but I don't think this is the case.

yeast is a type of fungi so therefore as vegan as any mushroom. can't see any reason to avoid it. in fact I would say it was important for vegans to eat it to get a good variety of B vitamins