The Torah recounts that as בני ישראל brought what would be their only קרבן פסח during their sojourn in the desert, there were individuals who were טמא מת and thus unable to participate. There is a discussion in the gemara (.סוכה כה) as to who in fact these individuals were. ר' יוסי הגלילי suggests they were the ones in charge of transporting יוסף's body. רבי עקיבא is of the opinion that it was מישאל and אלצפן who were instructed to remove נדב and אביהו bodies from the mishkan. Finally, רבי יצחק discounts the first two opinions and posits that these were individuals who had become tamei as a result of a מת מצוה.
It is somewhat intriguing that the approach taken in the גמרא is that there was something special and unique about this group. Although, it is not unusual for a midrashic source to fill in the blanks in a פסוק, even if there is no compelling evidence that there is something missing. However, there is a question to be asked on the first two opinions. Why is it that ר' יוסי and רבי עקיבא assume that these individuals were part of a single group, that they were all טמאי מת for the same reason? Could there not have been more than one cause for people to be טמא?
Perhaps they made an inference from the specific wording of the פסוק. The introduction to this story is as follows (9:6)
ויהי אנשים אשר היו טמאים לנפש אדם
One would have expected the פסוק to read "ויהיו" in the plural. But instead, the singular "ויהי" is used in reference to a group of people. Perhaps ר' יוסי and רבי עקיבא understand that the פסוק is specifically worded this way to convey that although there were a number of individuals were טמא, they were all טמא for the same reason.