Charles Forte speculated that this was waste dumps from passing space craft. ;-)
Or finished experiments: There were cases of large chunks of flesh, believed to be beef (hopefully) that fell in the UK in times past.
On a similar note, there's been frogs, fish etc. dropping in various places, always attributed to "tornadoes sucking up them up and depositing them elsewhere". Funny thing, they were pretty selective tornadoes as no other associated items like lily pads or other solid debris would come down. Hmmm. :-)