Spokesman Scott Wargo says the college approached the FBI with "significant concerns" about the incidents, which began the first week of February. He says the FBI notified Oberlin on Thursday that it would begin investigating.
Classes were canceled Monday after a report of someone wearing what looked like a Ku Klux Klan-type hooded robe on campus.
A police report has also detailed the defacement of Black History Month posters with the N-word, a "whites only" sign written above a water fountain, a swastika drawn on a science center window and a student knocked to the ground by a person making a derogatory comment about ethnicity. Two students are being investigated for possible involvement in the graffiti.