Robbinsdale police have launched an investigation into allegations that an employee at North Memorial Health Hospital sexually assaulted a 78-year-old patient there last week.

The patient told police that she was sexually assaulted sometime on Oct. 18 or 19, near the end of a weeklong stay at the hospital in Robbinsdale, according to an affidavit for a search warrant filed in Hennepin County District court. The victim, who did not immediately report the alleged assault, told police that after being discharged and checking into a health care facility in New Brighton, she "awoke from a nightmare, profusely swearing, and remembered in detail what had happened during the assault," the affidavit said.

The victim was later transferred to Fridley's Unity Hospital, where she underwent a sexual assault examination.

She described her alleged assailant as a white male in his 30s, about 6 feet tall, with shaved blonde hair and blue eyes, whom she recognized from previous interactions at the hospital, the affidavit said.

A North Memorial spokeswoman said Friday evening that the hospital was "unaware of the allegation."