She said CEO Bill Timmons, who resigned on Monday, told them not to report on an incident back in 1998.
The firm, which says it is cooperating with police, provides services ranging from day programs to long-term residential care for more than 2,500 patients annually.
A patient who had been in care at the facility for more than 10 years gave birth on December 29, a source told KPNX. According to the local station's unidentified source, the facility staff had no idea the patient was pregnant until she began moaning as she went into labor.
Gary Orman, the executive vice president of the company's board, said it would "accept nothing less than a full accounting of this absolutely horrifying situation".
In the statement, DHS spokesperson Melissa Blasius-Nuanez said the agency immediately initiated an onsite complaint investigation to "ensure the health and safety of the patients and ensure the facility is in compliance with all state laws and regulations".
The woman said not one person reported the incident out of fear, adding that it is likely other forms of abuse took place over the years. However, Spokeswoman Nancy Salmon of Hacienda Healthcare attempted to do damage control with the following statement.More news: Regional party quits India's ruling coalition over citizenship row
More news: Video shows Cody Parkey's field goal tipped by Eagles DT Treyvon Hester
More news: Record-setting Buckeyes quarterback Dwayne Haskins declares for NFL Draft
Cesena's daughter almost drowned 14 years ago and was left with a traumatic brain injury that caused her to have hundreds of seizures a day. "And they didn't know what was wrong with her. ..."
"I want to assure our patients, their loved ones, our community partners, the agencies we do business with, Governor Ducey and the residents of Arizona, we will continue to cooperate with Phoenix Police and the investigating agencies at all levels in every way possible", Orman said.
A female staff member said another female staff member "entered the room and just wanted to talk with [the other staff member]" who was giving the bath.
It happened at Hacidena Healthcare, a facility for medically fragile children, teens, and adults.
Hacienda almost lost its Medicare funding in December 2013 after Arizona Department of Health Services (ADHS) found at least one staff member was abusive to multiple patients while several staff members were deficient in reporting patient allegations of abuse by staff. In 2013, a male employee was found to have made sexually explicit remarks to patients, though no physical or sexual abuse allegations were made and the employee was sacked.
The health care facility has at least 74 patient beds, according to federal records.