V.T.
Hi J.,
I had the very same problem last year (except it was butter in the bottom of my oven). There is an oven cleaner that is for "Auto Cleaner Ovens". You can spray that in there, and clean up some of the mess.
I did that, and it helped! I actually missed some of the butter, b/c the second time I ran the oven, a smaller fire started, and then put it self out. . .. but the third time was uneventful!
Good Luck!