From Manx Radio website:

http://www.manxradio.com/readNEwsItem.aspx?id=24682

It seems there are some sad people who are "deliberately" allowing diesel onto the TT course.

I hope it's not true and that the spills are accidental, but the stuff we had last night was right along the racing line as opposed to where "normal" traffic would be.

Lets hope it's a coincidence...