Geisinger announced the results of a probe into a November computer security breach, blaming Vole-owned Nuance Communications for not cutting off one of its employees' access to corporate files after that person was fired.

The Pennsylvania-based healthcare giant uses Nuance as an IT provider. Two days after the Microsoft-owned entity fired one of its workers, that staffer may have accessed and taken copies of sensitive records on a huge number of Geisinger patients.

Geisinger, which says it operates 13 hospitals and has more than 600,000 members, said it discovered the improper access on November 29, informed Nuance, and the IT supplier immediately cut off the former employee from the healthcare group's data before involving police.

Geisinger said because it could have impeded their investigation, law enforcement investigators asked Nuance to delay notifying patients of this incident until now.

The former Nuance employee has been arrested and is facing federal charges.

Speech recognition firm Nuance performed a probe, according to Geisinger, and determined that the former employee may have stolen information on a million-plus people.

That info would include birth dates, addresses, hospital admission and discharge records, demographic information, and other medical data. The multi-billion-dollar healthcare group stated that the ex-employee didn't swipe insurance or other financial information.

Geisinger chief privacy officer Jonathan Friesen said, "We continue to work closely with the authorities on this investigation. While I am grateful that the perpetrator was caught and is now facing federal charges, I am sorry that this happened."