Massachusetts regulators revoked or suspended the professional licenses of 13 nurses after discovering recently that the health care workers lied about having nursing degrees or being licensed in other states, health department documents show.
The action sparked questions about the background checks state regulators rely on to issue licenses to thousands of nurses and applicants in 10 other health fields, including pharmacists, psychologists, podiatrists, and optometrists.
And the discovery raised the unsettling prospect that patients might have been treated by health care workers with fraudulent credentials, although regulators said there is no evidence so far linking the nurses to any patient safety or quality of care issues.
At least five of the nurses whose licenses were revoked had actually been working as nurses in Massachusetts, according to state documents. But health officials were unable to say where they had been employed.
The state health department said it has referred the apparent fraud cases to the FBI and the state attorney general's office. A health department spokesman declined to say whether officials believe the cases are related, and a spokeswoman in the attorney general's office declined comment.
The first hint of a problem emerged in late July when Nursys, a national database for verifying nurses' licenses, notified the Massachusetts Department of Public Health of potential fraud committed by two women licensed in Massachusetts.
Those two nurses, identified by officials as Edna Tunis of Roslindale and Jesula Eustache of Milton, had applied for licenses in Oregon. But the Oregon State Board of Nursing rejected their applications after finding both women had falsely stated they had passed a national nursing licensure exam, completed a nursing education program, and met the nursing practice requirement.
The women also wrote in their Oregon applications that they were licensed in Massachusetts, which would have allowed them to avoid taking Oregon's nursing examination under a system known as "reciprocity." Most state nursing boards waive testing requirements if applicants are already licensed in another state, and both women had received Massachusetts licenses, Eustache in January and Tunis in May.
After being alerted to the Oregon cases, the Massachusetts Board of Registration in Nursing suspended both women's licenses at an emergency meeting in early August. Tunis and Eustache admitted that when they sought licenses in Massachusetts, they falsely stated they had Alabama licenses, according to documents both signed in August.
The acknowledgment by the women of their fraudulent actions prompted members of the nursing board to wonder whether "a larger enterprise" had helped the nurses in their deception, according to minutes of that meeting.
Regulators embarked on a review of licenses recently granted to nurses who stated in their applications that they had licenses in other states. Investigators found 11 similar cases over the past year.
But after another instance emerged, dating to 2012, regulators extended their investigation of licences granted under reciprocity to 2010, according to the state health department. It was not clear whether any action was taken related to the 2012 case.
Last week, the Massachusetts nursing board suspended the licenses of seven nurses. Four others — Jeannot Maceus of Dorchester, Claudel Jean Baptiste of Brockton, Guerla M. Belony of Randoph, and Herold Philippe of Brockton — agreed to have their licenses revoked. They admitted to falsely stating they had licenses from other jurisdictions, including Puerto Rico, Louisiana, Hawaii, and Oklahoma.
"Upon learning about a problem with valid licenses, the Board of Registration in Nursing took decisive action to investigate and suspend the licenses of individuals who fraudulently represented that they were licensed in a reciprocating state," Scott Zoback, spokesman for the state health department, said in a statement.
State officials suggest that the fraud may have been possible because each applicant claimed to have licenses from one of eight states that do not fully participate in the Nursys online database used to verify licenses.
As a result, the company that Massachusetts employs to scour the backgrounds of nursing license applicants would have needed to search for paper records from those states.
That company, Professional Credentials Services of Nashville, also reviews applicants seeking Massachusetts licenses to work as chiropractors, occupational therapists, optometrists, pharmacists, pharmacy interns, pharmacy technicians, physical therapists, podiatrists, psychologists, and certified health officers.
In the wake of the discovery about the nurses' applications, the state health department said it is "currently evaluating" whether it will retain Professional Credentials Services for future work.
In the meantime, state regulators have asked Professional Credentials Services to immediately tighten its process for checking applicants' backgrounds, particularly for those claiming a license from another state.
Attempts late Friday to reach Professional Credentials Services, and its chief executive, Mark Setash, were unsuccessful.
State regulators said three of the nurses had completed education programs to become licensed practical nurses, but had falsely indicated they had more advanced training. Others listed nursing degrees from fictitious schools, regulators said.
Kay Lazar can be reached at Kay.Lazar@globe.com. Felice Freyer can be reached Felice.Freyer@globe.com.