The United Nations in Chad has launched an internal investigation, following a report by the Associated Press news agency on allegations of sexual exploitation of Sudanese refugees .

The statement, written days after the AP published the story, was seen on Tuesday (Nov. 26). It said the seriousness of the allegations cited in the AP’s story, warranted immediate and firm measures and that those responsible should be punished.

The U.N. did not immediately respond to questions about what the internal investigation entailed.

Speaking on condition of anonimity, Sudanese women and girls who found refuge in Chad alleged humanitarian workers and local security forces had sexually exploited them.

The men allegedly offered money, easier access to assistance or jobs.

The UN said it’s cooperating with local authorities and human rights groups to hold those responsible to account.

The organization said it raised the risk alert level for protection against sexual exploitation of abuse to four, which is very high, especially since Chad was already classified as a country at high risk. Raising the alert is meant to enable the U.N. to take rapid measures in the next three months, according to an internal email about the AP’s article, circulated among aid groups and seen by the AP.

The U.N. has encouraged anyone with information about exploitation to come forward.

Aid groups have long struggled to combat sexual exploitation during large humanitarian crises.

They have cited a lack of reporting by women, not enough funds to respond and a focus on first providing basic necessities.

Hundreds of thousands of people, most of them women, have streamed into Chad to escape Sudan’s bloody civil war.