CAMBRIDGE, Mass. — A local health care group says that it has notified patients of a data breach.

The Boston Globe reports that Cambridge Health Alliance informed 2,500 people that their private billing information was accessed by a third party.

Everett police made CHA aware that patient information had been compromised on Jan. 31. The organization didn’t notify patients until the end of March.

Officials do not know if the security breach was a result of a hack, or if the data was “inadvertently made public,” say hospital administrators.

While no medical records were made public, patients’ names, addresses, phone numbers, social security numbers and other information were accessed.

Health care group spokesman David Cecere says an investigation into how the breach happened is ongoing.