Lauren Mann, 25, had been living in the Austrian capital and was working as an au pair, or nanny, for a local family. She was found dead in a pool of blood on Tuesday at 6 p.m. in her apartment, according to Vienna police. Her body was half-undressed, according to Thomas Keiblinger, a Vienna police spokesperson.
Today, the city's prosecutor Nina Bussek told ABC News that Mann had suffocated. Investigators have not yet determined if someone else was involved in her death.
Keiblinger previously told ABC News that a preliminary autopsy showed Mann has not been stabbed or strangled and there were no external wounds on her body.
There are no suspects or arrests at this time, according to police. Officers have been in contact with Mann's friends.
The family for whom Mann worked said in an interview that Mann was "very reliable, trusted, caring and socially active." Family members became concerned when one of their children was not picked up from school on Monday.
Mann's neighbor Peter Kratochwill told ABC News it was "extraordinary" for something like this to happen in "a neighborhood that is so quiet and safe."
The U.S. Embassy in Vienna is providing consular assistance.
ABC News' Louise Dewast contributed to this report.