Hundreds of private medical records have been found strewn across a room and easily accessible to the public in an abandoned healthcare facility in the Australian State of New South Wales (NSW).

Local media outlet ABC uncovered the records in an investigation, and was reporting on Friday that it is the largest private information breach of its kind.

The derelict building used to be an aged care facility which NSW Health said was illegally accessed by journalists who ignored asbestos warnings.

However, the Australian Privacy Foundation's health committee chair Dr Bernard Robertson-Dunn told the ABC that an appropriate explanation was needed.

"For NSW Health to claim the site was (accessed illegally) is a little weak," Robertson-Dunn said.

"You have to look after health data very carefully."

The documents pertain to nearly 400 patients from 1992 to 2002, of whom the ABC are reporting, the majority -- if not all -- are dead.

NSW health minister Brad Hazzard said that the matter is being looked into.

"To those people whose medical records were put in such storage arrangements in the early 2000s, I express my sincere apologies and can assure them and their families I will get NSW Health to do whatever I can to rectify the situation."