Cell clumps or contamination? Please help! - (May/22/2015 )

Hello!

I am in dire need of some advice. Basically, I transfected cells (with just a fluorescent marker to identify cells in a coculture) and now my cells sometimes grow in huge clumps and will occasionally break off in these huge clusters. I am confused as to why this happens. The pH doesn't change, the clumps do not move and are the same size as cells (as in the individual 'things' in the clumps are the same size as cells - not the whole clumps). They seem to be attached to the cells that are adhered to the flask but sometimes I have these bizarre clump chains coming off from my adhered cells... Could this be contamination? I feel like they are too large to be contamination but do not have experience with this so am not sure. Please help, it is driving me crazy!

Thanks! 

What sort of cells and what are your culture conditions?