SACRAMENTO (AP) — An analysis of a federal investigation of the UC Davis Medical Center — conducted after the deaths of three brain surgery patients at the facility — found that hospital policies and federal regulations were violated, The Sacramento Bee reported Sunday.

The 92-page report released earlier this month by the Centers for Medicare and Medicaid Services, found that besides the alleged violations, investigators found hospital staff repeatedly failed to intervene or raise questions about the unusual surgeries on the three brain cancer patients, the newspaper said.

“(T)he hospital failed to effectively govern the activities and conduct of the hospital staff to provide safe and quality care to all patients,” the report by the watchdog agency said, and described the hospital’s problems as “systemic failures.”

The three cases involved two neurosurgeons implanting bowel bacteria into patients’ brains — work that received so little scrutiny that the agency concluded all UC Davis hospital patients were at increased risk for infections and even death, The Bee said.

The Bee first reported in July that surgeons J. Paul Muizelaar, 65, the former chairman of the neurological surgery department, and Rudolph J. Schrot, 44, had begun working on a procedure to treat brain cancer patients with a novel procedure involving live bacteria.

In 2010 and 2011, three patients with deadly glioblastomas consented to have their skulls opened and intentionally infected with Enterobacter aerogenes, the bacteria commonly found in the gastrointestinal tract, the newspaper said.

Use of experimental drugs or devices in humans is tightly regulated and must undergo a rigorous review process by both the research institution and government agencies, The Bee said.

The UC Davis neurosurgeons are accused of sidestepping those processes with their “probiotic intracranial therapy,” an untested procedure based on their theory that postoperative infections might stimulate patients’ immune systems and prolong their lives, The Bee reported.

The bacteria, though, were not approved for use in humans and had been purchased for the doctors’ study involving lab rats, according to university and federal documents.

Only after the third patient was treated in March 2011 — and died 14 days later of sepsis, a severe bodily reaction to infection — did the university order the neurosurgeons to “cease and desist,” The Bee said.

Both Muizelaar and Schrot still have their positions at the medical center, though Muizelaar recently took a leave of absence from clinical work, The Bee said.

Attempts by The Associated Press to reach Muizelaar and Schrot for comment were unsuccessful.

University officials have rejected the findings of the report and say patient care at the medical center remains “excellent.”

Medical center officials did not immediately provide comment to The Associated Press about the report.