Des Forges, 66, was a passenger on a Continental Airlines commuter plane that crashed Thursday night as it approached the Buffalo Niagara Airport. Des Forges, who lived Buffalo with her husband, a professor at the University of Buffalo, was returning from a trip to Europe, the group said.

A graduate of Radcliffe College, Des Forges wrote her Ph.D. thesis at Yale on Rwanda. She began working for Human Rights Watch as a volunteer and Kenneth Roth, the executive director, said he had to force her to take a salary.

“She was truly wonderful, the epitome of the human rights activist — principled, dispassionate, committed to the truth and to using that truth to protect ordinary people,” Roth said.

Des Forges testified at trials on the 1994 genocide. But she also exposed abuses by the Rwandan Patriotic Front, now the government, and was banned from the country in 2008.

She received a MacArthur Award in 1999, the same year she wrote an award-winning report on Rwanda, “Leave None to Tell the Story.”