On Wednesday night, RCMP officers went door-to-door on Gitzel Street, near where the offence occurred.
A Gitzel resident, who asked not to be named, said the RCMP described the offence as fairly violent.
"Any sexual assault is violent," said Sgt. Al McCambridge of the Yellowknife RCMP.
McCambridge refused to release details about how or where the offence occurred, or any description of the offender beyond "a young adult male wearing dark clothing."
However, the resident of Gitzel who spoke to RCMP, said the suspect was described as 5'5" in his late teens or early 20s.
McCambridge said the RCMP told local schools about the investigation and asked them to remind their students of general safety guidelines, such as not talking to strangers, or walking alone at night in dark places.
Principal Adrian Amirault of Mildred Hall school said the school's RCMP liaison officer asked the school to do a safety talk.
Despite reports on a local radio station that RCMP have confirmed they are investigating a second sexual assault, McCambridge said that there was no second assault.