Aid workers of charity organisation Medecins Sans Frontieres (Doctors Without Borders) allegedly paid for sex while working in Africa, BBC reported on Thursday citing whistleblowers. The non-governmental organisation said it took the allegations seriously but said it had been unable to confirm the claims.

A former employee who worked at the charity’s London office told the BBC that she had seen a senior staff member bring girls back to the MSF accommodation while posted in Kenya. “The girls were very young and rumoured to be prostitutes,” she said, adding that it was “implicit” that they were there for sex. She also said that her colleague who stayed at the same residence felt “this was a regular occurrence”.

The whistleblower said they felt unable to challenge the man “because he was quite senior”.

Another woman employee who worked with HIV patients in central Africa said the use of local sex workers was widespread. She said she also felt sexually harassed by some of the men she worked with.

A third whistle-blower described how a senior colleague boasted of trading medication for sex with girls in Ebola-hit Liberia. “He was suggesting lots of the young girls who had lost their parents to the Ebola crisis, that they would do anything sexual in return for medication.” The BBC, however, said it had not been able to verify the allegation.

The whistleblower also claimed that on other occasions MSF workers had sexually harassed partners at other non-governmental organisations.

Executive Director of MSF UK Vickie Hawkins said the organisation has reporting mechanisms in place where complaints can be made, but “we know we need to do more to ensure that they are known, trusted and used by the people who need them.”

These allegations come just a week after Haiti permanently banned the British unit of international charity organisation Oxfam from operating in the country after reviewing sexual misconduct allegations against some of its employees.

Former aid workers of Oxfam – one of the United Kingdom’s biggest charities – are accused of paying for sex while on a mission to the Caribbean nation in 2011 to help those affected by the devastating earthquake the year before.