NAIROBI, Kenya — The American ambassador to the United Nations, Nikki R. Haley, on Thursday urged the organization to go beyond its inquiry into the killings of two investigators in the Democratic Republic of Congo, saying that the U.N. report amounted to only a “first step” in tracking down those responsible.

The United Nations issued a report on Wednesday that largely absolved the organization from responsibility over the deaths, in March, of Michael J. Sharp, an American, and Zaida Catalán, a citizen of Sweden and Chile. The report concluded that the two had ignored security measures available to them while they conducted their investigations. It also implied that they lacked experience.

“The murder of U.N. experts — especially like Michael and Zaida, who risked their own lives in order to help others — cannot end in a bureaucratic procedure,” Ms. Haley said in a statement. She reiterated American demands for “a full investigation.”

“There is simply no other appropriate course of action,” she said.

The deaths of Mr. Sharp, 34, and Ms. Catalán, 36, raised questions about the United Nations and its work in the most dangerous places in the world. Almost two months passed before the United Nations even assembled a panel to look into what went wrong, and its members traveled to Congo only in early June.