The assault of a black Oregon college student by three white students is being investigated by a police hate crime unit and comes days after Portland police received reports of racist threats on social media, authorities said on Monday.The 26-year-old black man was assaulted on Friday night by three white men near the campus pool at Lewis & Clark College in Portland, police said."The victim told police that the suspect used racial epithets before assaulting him," Portland Police Department spokesman Pete Simpson said in a statement. "The victim fought back and was able to get away and go to his residence on campus."The attack came just days after Portland police received reports of racist remarks and threats over the social media app Yik Yak directed at students and staff at Lewis & Clark, a small, private liberal arts school.Simpson said detectives who investigate bias crimes have opened a probe into both incidents and it was not yet known whether they are related.The assault also comes about one week after a male student was charged with making threats through Yik Yak against black students at Michigan Technological University. Similar online threats have also targeted students in Missouri and in Washington, DC.