Police have served a search warrant to obtain DNA from every male employee at a long-term care facility in the United States where a patient who had been in a vegetative state for years gave birth.

Key points: The woman has been in a vegetative state for more than 10 years after a near-drowning

The woman has been in a vegetative state for more than 10 years after a near-drowning In the wake of the reports, new safety measures have been implemented

In the wake of the reports, new safety measures have been implemented The facility has been subject to multiple complaints going back to 2012

The search warrants were served following the resignation of Hacienda chief executive Bill Timmons at the facility in Phoenix, Arizona. The resignation was unanimously accepted by the provider's board of directors.

Local news website Azfamily.com first reported the woman, who had been in a vegetative state for more than 10 years after a near-drowning, delivered a baby on December 29.

San Carlos Apache officials have announced the 29-year-old woman was an enrolled member of the tribe, whose reservation is in south-eastern Arizona about 215 kilometres east of Phoenix.

Hacienda HealthCare said it welcomed the DNA testing of employees.

"We will continue to cooperate with Phoenix Police and all other investigative agencies to uncover the facts in this deeply disturbing, but unprecedented situation," the company said in a statement.

In a statement, tribal officials said the woman was still in a coma when she gave birth.

The woman's name was redacted from the tribal statement, and there was no information about the gender or status of the baby.

It's not known if the woman has a family or a guardian.

It's also unclear if staff members at the Hacienda de Los Angeles facility were aware of her pregnancy until the birth.

"On behalf of the tribe, I am deeply shocked and horrified at the treatment of one of our members," tribal 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. It is my hope that justice will be served."

San Carlos Apache Police chief Alejandro Benally said Phoenix police "will do all they can to find the perpetrator" and his department will assist "in any way possible."

In a statement, board member Gary Orman said the facility "will accept nothing less than a full accounting of this absolutely horrifying situation."

"We will do everything in our power to ensure the safety of every single one of our patients and our employees," Orman said.

Governor Doug Ducey's office called the situation "deeply troubling".

Phoenix police said the matter was under investigation and declined further comment.

The Hacienda facility serves infants, children and young adults who are "medically fragile" or have developmental disabilities, according to the website.

In the wake of the reports, the Arizona Department of Health Services said new safety measures had been implemented.

They include increased staff presence during any patient interaction, more monitoring of patient care areas and additional security measures involving visitors.

Employee fired for sexual comments about patients

The state's online complaint database for care facilities shows multiple complaints about Hacienda de Los Angeles going back to 2013.

Most of them involve fire drill and evacuation preparation or Medicaid eligibility.

But one complaint from December 2013 outlines an allegation that a staff member made inappropriate sexual comments about four patients two months earlier.

Nobody relayed the incidents to an administrator. That employee was later fired.

Martin Solomon, a personal injury attorney in Phoenix whose clients are mostly vulnerable adult victims of abuse and neglect, said a lawyer representing this woman should call for all pertinent medical records, a list of current and ex-employees and any past litigation involving Hacienda.

It would be the police who would lead DNA testing to figure out who fathered the baby, Mr Solomon said.

AP