Police in Arizona are seeking DNA samples from male staff at a nursing home where a patient in a vegetative state gave birth.
The incident occurred at a clinic run by Hacienda HealthCare, near Phoenix.
The centre said a warrant was served by police on Tuesday, as authorities try to find out how the woman became pregnant.
She has reportedly been a patient at the facility for at least a decade following a near-drowning incident.
Earlier this week, the chief executive of the corporation in charge of the home resigned over the case.
In a news conference on Wednesday, Phoenix police spokesman Sgt Tommy Thompson said it was not known whether anyone had declined to give a DNA sample.
On its website, Hacienda HealthCare says it provides care for “medically fragile and chronically ill infants, children, teens, and young adults as well as those with intellectual and developmental disabilities”.
The female patient, who has not been identified, reportedly gave birth to a boy on 29 December.
Police said the infant was not breathing when they were called into the facility, though both mother and child are now recovering in a local hospital.
Lawyer John Micheaels, representing the woman’s family, described her as being in a “completely vulnerable state”.
“The family obviously is outraged, traumatised and in shock by the abuse and neglect of their daughter at Hacienda HealthCare,” the attorney told NBC’s 12News.
The relatives, who say they are not ready to come forward, asked for it to be conveyed publicly that the child has been “born into a loving family and will be well cared for”.
The woman is a member of the San Carlos Apache Tribe, according to a statement released by tribal leaders on Tuesday.
“I am deeply shocked and horrified at the treatment of one of our members,” Tribe Chairman Terry Rambler said.
“When you have a loved one committed to palliative care, when they are most vulnerable and dependent upon others, you trust their caretakers. Sadly, one of her caretakers was not to be trusted and took advantage of her.”
Local media reports say staff at the care home were unaware the patient was pregnant until she gave birth.
Hacienda has said it will “do everything in [its] power to bring this police investigation to a quick conclusion”.
“We will continue to co-operate with Phoenix police and all other investigative agencies to uncover the facts in this deeply disturbing, but unprecedented situation,” it said in a statement.
The company also said it had sought legal advice over the possibility of mandatory DNA testing for staff, but was advised it would violate federal law.
Arizona Department of Health Services said additional safety measures have been implemented at the home since the case came to light.