The BBC has this story on their site aswell, its refering to a press confrence six hours after the 'Top Kill' operation began. BP think that the
stuff you can see coming out of the riser is the drilling mud that they are pumping into the Blow out Preventer.
It reads it SEEMS to be only mud - like someone would say 'Geesh that's so thick and black it looks like mud'...
AND it goes on to say they are not sure, because they cannot test it. They can't get a sample to test.
So basically all you got is someone saying - 'What a mess. If we could test it we might be able to tell you what it is, but until then it sure looks
like mud.'