PORT-AU-PRINCE, Haiti – It began as a rumor that farmers saw waste from a U.N. peacekeeping base flow into a river. Within days of the talk, hundreds downstream had died from cholera.

The mounting circumstantial evidence that U.N. peacekeepers from Nepal brought cholera to Haiti was largely dismissed by U.N. officials. Haitians who asked about it were called political or paranoid. Foreigners were accused of playing "the blame game." The World Health Organization said the question was simply "not a priority."

But this week, after anti-U.N. riots and inquiries from health experts, the top U.N. representative in Haiti said he is taking the allegations very seriously.