VIENNA (CBS4)– An autopsy failed to give investigators clues as to how a Colorado woman who was working as an au pair in Vienna died.

Lauren Mann’s body was discovered on a mattress inside her apartment on Tuesday after she failed to show up for work as a nanny on Monday. Her employer called police.

Investigators are waiting for the results of toxicology tests to determine whether she was poisoned.

Mann, 25, was from Paonia, a small town in Delta County in western Colorado. She graduated from the University of Colorado in 2012.

Police said all the light bulbs in her apartment were burned out.