The United Nations has spent half a billion dollars on contracts with a Russian aviation company since discovering one of its helicopter crews in the Democratic Republic of the Congo drugged and raped a teenage girl in a sexual attack. The girl was dumped naked and unconscious inside the helicopter base. Internal UN documents, marked strictly confidential" and leaked to the Guardian, reveal how the UN's internal complaints unit uncovered evidence the woman was abused ... by the manager in charge of UTair's base in Kalemie, eastern DRC. The main investigative report, from March 2011, warned of a possible "culture of sexual exploitation and abuse" at UTair. Copies of that report were circulated among top officials at the UN. The company was permitted to continue doing business with the UN on the condition it introduce a new training regime overseen by a monitor. The disclosures come at a critical moment for the UN secretary general, who has struggled to contain the fallout from recent revelations concerning the sexual abuse of children by French and other peacekeeping troops in the neighbouring Central African Republic. "It wasn't just one or two bad apples," said a senior UN official familiar with the report and its fallout. "It was clear the problems of sexual exploitation were wider." In total, the company ... has been granted contracts worth $543.3m for services provided in 11 countries since the UN became aware it had a problem with sexual exploitation.