Matrigel contamination - (May/31/2012 )

Hi,
We have recently had an unknown problem with our human stem cells cultured on Matrigel. The contaminant was attached to the Matrigel, with some of the ends waving freely in the media. All the cells in the culture were dead, though this may have been to another cause.
The attached image at 40x shows the unknown dark matter. Any help in identifying the contaminant is appreciated. Thanks!

That is one serously out of focus photo - but my guess would be bacterial based on the small dots floating around.