The body of 25-year-old Lauren M. was discovered after her employee informed police when she realised the normally reliable au-pair had not picked up her child from school.
Firemen broke down the door to her flat to find her half-undressed body lying face down on a mattress and surrounded by burning candles. Although investigators believed she had been suffocated it was too soon at that time to tell whether she had definitely been murdered.
Spokesperson for the state prosecutors Nina Bussek confirmed to the Kurier newspaper on Wednesday that they are now sure they are dealing with a murder case and that Lauren M. was forcibly suffocated to death.
The newspaper also reported that DNA belonging to a suspect who had been living in the apartment with the American was found on her body.
Gambian Abdou I., 23, who had been living with Lauren M. after his asylum application was rejected by authorities, disappeared after her body was discovered but was soon arrested in a Swiss asylum centre.
Last week a Swiss judge ruled that he can be extradited to Austria, although he has 30 days to decided whether or not to lodge an appeal.
If no appeal takes place, he will be deported in April.