A federal watchdog agency is investigating the case of two neurosurgeons at the University of California at Davis whose patients died while undergoing an experimental treatment for brain cancer, leading the doctors to be barred from conducting research on human subjects. The university confirmed this week that the Centers for Medicare and Medicaid Services, an agency in the U.S. Department of Health and Human Services, had asked the state to review the care of the physicians’ patients, according to The Sacramento Bee. The doctors introduced bacteria into three consenting patients’ open head wounds, theorizing that the subsequent infections would trigger an immune response to fight the cancer. Two of the patients developed sepsis and died within weeks, and the third died months afterward. A university spokeswoman said the findings of the inquiry, by the California Department of Public Health, are expected in about a month.