Senior US lawmakers have called for an investigation after BuzzFeed News revealed the World Wide Fund for Nature bankrolls anti-poaching forces who have tortured and killed indigenous people.

WWF says that 1.2 million of its nearly 5 million donor members are in the United States, and the charity partners with federal agencies such as the United States Agency for International Development.

“I strongly support efforts to combat wildlife trafficking, but this must not come at the cost of the health, safety, or life of innocent civilians,” Rep. Eliot Engel, the chair of the House Foreign Affairs Committee, said in a statement. “If this reporting is accurate, WWF should do whatever it takes to root out the problems and demand accountability.”

Sen. Patrick Leahy, a Vermont Democrat who actively supports American aid programs overseas, also called for an “immediate and thorough review” of US support for WWF in the wake of the “shocking” revelations. “We all want to protect endangered species and law enforcement is an essential part of that, but it needs to be demonstrated that local park guards are properly trained and monitored, and that those who commit abuses are held accountable,” he said.

BuzzFeed News reported on Monday that in national parks across Asia and Africa, WWF funds, equips, and works directly with paramilitary forces that have been accused of beating, torturing, sexually assaulting, and murdering scores of people. WWF launched an “independent review” in response to the revelations. The law firm Kingsley Napley will conduct that review, the Guardian reported Monday.

The US Fish and Wildlife Service, which funds and partners with WWF on conservation programs, said: “We are monitoring this situation closely and will do everything in our power to ensure the rights, health and safety of those who reside in areas where we provide financial support for wildlife conservation.”

USAID said it “holds its partners to the highest moral standards” and has “zero tolerance” for abuses.

On Monday, Members of the UK Parliament called for an investigation into the British government's funding of WWF, and celebrity explorer Ben Fogle announced he had suspended his role as an ambassador for the charity in response to the BuzzFeed News story.

The United Nations’ special rapporteur on the rights of indigenous peoples, Victoria Tauli-Corpuz, said she found it “regrettable that such incidents have happened.”

“I hope that the independent investigation will come up with initial evidence and redress should be provided to people who have been victimised,” Tauli-Corpuz said.