Many U.S. colleges are clamping down on campus fraternities after their reputations are sullied by race-tainted incidents.

Even with a school's sometimes swift and hard action, episodes such as the racist chants by members of the Sigma Alpha Epsilon chapter at the University of Oklahoma still surface.

In recent years, numerous other fraternities have been suspended and students expelled from school for racially tinged parties or behavior. Actions have included hanging nooses and shouting racial profanities.

Many incidents come to light after the students themselves post pictures or videos online, drawing public attention.

Defenders of fraternities point to the system's charitable works and social and professional benefits for members.

But beyond racism, fraternities in recent years have had to confront issues of sexual assault, binge drinking and hazing among members.