Processing error, possibly foreign body splatter while the film was wet. Inspect the film edgewise to see if there are particles stuck to it. I've never used that film. What was the developer and how was it mixed? Being white on the positive image the spots would be caused by something that blocked the light. You might try cleaning the film with something like PEC 12, refix and rewash. Be sure to dry it in a dust-free environment.
That's the best I can come up with.