Currently there is only ogg and wav support
Although these are the most common ones, a lot of other formats are supported, so it's probably better if you say "Currently there is no support for MP3" 
Good point.
Here is the list of formats in the faq--I don't know if there are any more:
ogg, wav, flac, aiff, au, raw, paf, svx, nist, voc, ircam, w64, mat4, mat5 pvf, htk, sds, avr, sd2, caf, wve, mpc2k, rf64