The supervisor called security, and officers, finding semen on the floor and wall, called the police, setting off the quick chain of events that led to police officers escorting Mr. Strauss-Kahn off an Air France plane set to depart Kennedy International Airport.

Suspicions of the woman’s associations arose relatively quickly: within a week of Mr. Strauss-Kahn’s arrest, the authorities learned of a recorded conversation between the subject of a drug investigation and another man, who said his companion was the woman involved in the Strauss-Kahn matter, according to another law enforcement official.

Prosecutors and investigators interviewed the woman at length.

Her immigration history was a focus. At first, she told them what she told immigration officials seven years ago in her accounts of how she fled Guinea and her application for asylum on Dec. 30, 2004. She described soldiers destroying the home where she lived with her husband, and said they were both beaten because of their opposition to the regime. She said her husband died in jail.

But then, in a subsequent interview with Manhattan prosecutors, she said the story was false, one she had been urged to tell by a man who gave it to her on a cassette recording to memorize. She had listened to the recording repeatedly.

The housekeeper also told investigators that she had been gang raped in Guinea. She cried and became “markedly distraught when recounting the incident,” according to a letter to the defense from prosecutors released Friday. But she later admitted that that, too, was a lie, once again one she had told to help her application for asylum. She said she was indeed raped in Guinea, but not in the way she had described.