The U.S. House Natural Resources Committee is seeking answers from an environmental activist group on alleged human rights abuses that include torture, sexual assault, and extrajudicial killings in their campaign to combat wildlife poaching.

Committee Chairman Raul Grijalva (D-Ariz.) and Ranking Republican Rob Bishop (R-Utah) sent a letter to the World Wildlife Fund (WWF) requesting documents about how the group operates after a Buzzfeed News story revealed that WWF “funds guards who have tortured and killed people.”

According to Buzzfeed, the group has hired, armed, and equipped forest rangers who have attacked local villagers in Asia and Africa with machetes and bamboo sticks and have sexually assaulted and murdered people. They have also organized and financed spy networks that rely on “fear” and “revenge,” and use slush funds to pay informants.

The story documents instances of WWF working with national governments in Cameroon and the Central African Republic to hire soldiers who were accused of killing unarmed civilians and embezzling money during arms deals. In Nepal, WWF praised the decision by the government to drop the case against parks rangers who were accused of murdering a suspected poacher who was never formally charged by authorities.

In a letter to WWF, Grijalva and Bishop write, “Despite the importance of protecting wildlife and preventing species extinction, the United States cannot be party to violations of basic human rights. More, such abuses undermine local support for wildlife conservation efforts and may jeopardize long-term species recovery.”

The committee is requesting a number of documents including WWF reports on its operations in Cameroon and Republic of the Congo, documents describing anti-poaching grants, contracts, and loans awarded by the U.S. Government, and the group’s policies, procedures, and training materials.

In addition to the letter, the Natural Resources Committee also said Grijalva and Bishop “requested a Government Accountability Office investigation of protections in place to prevent federal funds from contributing to human rights abuses including torture, sexual assault, and extrajudicial killings associated with anti-poaching efforts. They have also requested a briefing from the Department of the Interior.”

The WWF told Buzzfeed News that human rights abuses are unacceptable and never justified, and it pointed to a written policy that says it will not “undermine” the basic human rights of indigenous peoples. The group also said it launched an “independent review.”

In addition to Grijalva and Bishop, other lawmakers have also called for an investigation into WWF including Rep. Elliot (D-N.Y.), Chairman of the House Foreign Affairs Committee, and Sen. Patrick Leahy (D-Vt.).

Over the past year, members of the House Natural Resources Committee have raised concerns about several environmental groups working in other nations. Last October, lawmakers sent letters to Center for Biological Diversity and EarthJustice questioning requesting documents regarding the group’s relationship with foreign actors in an attempt to block a plan by the U.S. Department of Defense to move the location of the military base on Okinawa, Japan, and coordination with China’s Communist Party.