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A long-term care facility in Arizona where a woman in a vegetative state gave birth last month has hired a private attorney to conduct an internal review to determine how the patient was impregnated.

Phoenix police have already executed a search warrant seeking DNA samples from male staff members at the Hacienda HealthCare center, where a woman who has been in a vegetative state for years gave birth to a baby boy. The Arizona Department of Health Services and the state's Department of Economic Security are also working with police in the investigation.

On Sunday, Hacienda HealthCare announced that it had hired former Maricopa County Attorney Rick Romley to additionally conduct an "exhaustive" internal review.

"Mr. Romley will have unfettered access to every facet of Hacienda’s business — including all the records related to this matter," said a statement from Hacienda. "We will do everything we can to aid this review and, once it is complete, to make sure this unprecedented situation never, ever happens again."

Romley said during a news conference Monday that he almost didn't take on the investigation because "when you begin to do these internal reviews, you find out things that maybe you did not know. And I was not going to be one that basically buried it."

But he was assured by Hacienda leadership that they would welcome his findings and make necessary changes.

Romley said he would be looking specifically at security and culture at the facility "to correct the horrendous facts that led up to the impregnation of this young woman."

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"If you’re not going to be repeating history, you have to know that that history was," he said, adding that he couldn't predict how long the investigation would take.

When asked about Hacienda's recent history of poor ratings, Romley said Hacienda leadership told him a severe drop in ratings from reviews conducted by the Arizona Health and Human Services were due to misreporting by the state.

But Romley said he is not "taking anything at face value."

According to a letter from U.S. Representatives from Arizona, Ruben Gallego and Tom O’Halleran, Hacienda has a 1 out of 5 rating from the state.

The letter said that more than 15 percent of patients at Hacienda report pain, in comparison with a national average of 5.7 percent. Nearly 8 percent of Hacienda patients have been physically restrained, while the national average is .3 percent, the letter said.

Caregivers for the woman were unaware that she was pregnant until she started to moan before giving birth on Dec. 29, an unidentified source told NBC affiliate KPNX and 911 calls made after the baby was born.

A person is considered in a vegetative state when they are awake but not showing any signs of awareness, according to the Brain Foundation.

The woman is non-verbal and incapable of moving on her own after suffering a near-drowning incident. Romley said Monday that she has been at the facility since she was 3 years old.

The San Carlos Apache Tribe said Tuesday that the patient is 29 and an enrolled member of its tribe.

An attorney for the woman’s family said in a statement to KPNX that the baby "has been born into a loving family and will be well cared for."

"The family obviously is outraged, traumatized and in shock by the abuse and neglect of their daughter at Hacienda HealthCare," the attorney said.

Hacienda HealthCare is privately owned and has more than 40 Phoenix-based health care programs that serve 2,500 people a year, according to its website. A majority of its patients are infants, children, teens and young adults.

The facility's chief executive, Bill Timmons, resigned Monday amid the investigation into the woman's case.