Turns out the one spreading the rumors was Hashimoto, who did so at the behest of Sakayanagi. Shortly thereafter, Sakayanagi appears before Class C and she informs them she has evidence regarding the rumors about Ichinose.
Some people from Class A 
just barged into Class B!
!اقتحم أشخاصٌ من الفصل أ الفصل ب
Die aus der A haben die B gestürmt!
¡Los de la clase A fueron a la clase B!
¡Los de la clase A han ido a la clase B!
Les élèves de la classe A
s’en prennent à la classe B !
Quelli della A
Algumas pessoas da Turma A acabaram
de entrar na sala da Turma B!
Там «А»-шники толпой
к «Б»-шникам пошли!