A House committee has formally requested an investigation into whether federal conservation funds support anti-poaching guards implicated in human rights abuses, citing a recent BuzzFeed News investigation that revealed that indigenous people had been tortured and killed by forces funded by the World Wide Fund for Nature (WWF).

In a bipartisan letter, Arizona Democrat Raúl M. Grijalva and Utah Republican Rob Bishop — the highest-ranking members of the Committee on Natural Resources — asked the Government Accountability Office, a federal watchdog, to “examine” the issue.

“Despite the importance of protecting wildlife and preventing species extinction,” the letter says, “the United States must not be party to violations of basic human rights.”

The GAO is asked to answer six questions, including whether government money goes to “partner organizations” that have backed forces accused of human rights abuses. The BuzzFeed News investigation found that WWF funds, equips, and works directly with paramilitary forces that have been accused of beating, torturing, sexually assaulting, and murdering scores of people.

The letter also asks how much federal agencies monitor for potential human rights abuses, and what enforcement actions the government takes if a partner organization is found to have supported “improper activities.”

The letter notes that Congress has spent hundreds of millions of dollars combating wildlife trafficking in recent years. WWF is one beneficiary, partnering with federal agencies such as the US Agency for International Development in conservation projects around the world.

The request is the latest in a series of international demands for further scrutiny of anti-poaching efforts after BuzzFeed News’ investigation. Politicians in the US and UK have called for their governments to investigate whether aid money has been used to fund forces accused of human rights abuses. The UK Charity Commission said it was opening a formal investigation into allegations of “atrocities and human rights abuses,” which it described as “at odds with everything we associate with charity.”

Earlier this month, an internal WWF investigation found that the German branch of WWF must overhaul its human rights policies. WWF International has also commissioned its own review led by the law firm Kingsley Napley and overseen by a former UN special rapporteur for human rights.