(CNN) When a woman who has been in a vegetative state for years suddenly gave birth at an Arizona care facility last month, caregivers were taken completely by surprise, telling 911 dispatchers, "We had no idea she was pregnant."

Phoenix police released audio of the frantic 911 call a nurse at the Hacienda HealthCare facility made after the 29-year-old woman gave birth on December 29. She has been a patient there since 1992, according to court records.

Police are treating the case as a sexual assault investigation and have begun gathering DNA from men who work at the facility. But there is currently no suspect in the abuse of the woman.

'We were not prepared for this'

The audio of the 911 call, obtained by CNN affiliate KNXV , paints an image of a frantic scene as workers rushed to save the baby boy, who was not breathing and "turning blue." All the names were redacted.

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