BOSTON (AP) – Four Massachusetts hospitals failed to adequately ensure their doctors were free of infectious diseases before allowing them to practice, according to federal investigators probing the case of a physician who worked for six months while she had tuberculosis.

Boston Medical Center, the principal assignment of the surgical resident, didn’t follow up after tests indicated she had tuberculosis, according to the U.S. Occupational Safety and Health Administration.

OSHA also concluded that three other hospitals where the doctor worked – Brockton Hospital, Cape Cod Hospital, and the VA Boston Healthcare System – didn’t have any way to gather detailed information on the health of trainee doctors before allowing them to start rotations, The Boston Globe reported.

The Globe obtained the findings, issued to the hospitals in August and September, through the federal Freedom of Information Act.

Officials have never identified the doctor, citing federal privacy laws. She was suspended from treating patients at Boston Medical Center in June. A Boston Medical spokeswoman would not provide any information about her, including whether she had returned to work there.

The federal investigation found the doctor tested positive for tuberculosis as part of a medical review required before she could start at Boston Medical Center. She was referred to a city clinic for an X-ray and other exams, but skipped the appointment. She then continued to work at the four hospitals.

Disease trackers have said they believe the woman was infectious from December 2004 through June. Once her illness was discovered, nearly 5,600 patients and healthcare workers were tested for tuberculosis.

Investigators concluded that four patients and 13 healthcare workers who tested positive for tuberculosis were probably exposed to the bacterial illness by the doctor, said Dr. Anita Barry, chief disease tracker at the Boston Public Health Commission. None of them have shown symptoms of the disease – which include a cough, high fever and fatigue – meaning they aren’t currently capable of spreading it. A small percentage of those with latent tuberculosis eventually become infectious.

There is no evidence the Board of Registration in Medicine, which regulates doctors’ behavior, has taken any action against the unnamed doctor, the Globe reported. None of the four hospitals face sanctions. All said they’ve taken steps to prevent a repeat of the problem. Boston Medical now requires that healthcare workers complete all the steps of tuberculosis testing before they can begin work. Previously, they could work after receiving the first phase of the skin test.

At Brockton and Cape Cod hospitals, all medical staff must provide full documentation that they do not have tuberculosis. The previous policy assumed that a resident’s home hospital had completed screenings for the disease.

“We’re all learning from our experiences, and we think we’re going to do a good job in making sure this doesn’t happen again,” said Dr. Michael Charness, chief of staff for the Boston VA Healthcare System.