The ABC and the government have agreed on the return of thousands of sensitive documents obtained by the national broadcaster that were meant to remain secret for at least another decade.

The Department of Prime Minister and Cabinet announced it had struck a deal with the ABC for the secure return of the documents on Thursday night.

"This has been achieved without disclosure of the ABC's source and by way of acknowledgement of the Commonwealth's national security interests," a press release on the agency's website said.

The ABC revealed on Wednesday that papers covering details of five federal government cabinet meetings over a decade had been unsuspectingly sold off in a locked filing cabinet at a second-hand shop in Canberra, which stocked ex-government furniture.

The filing cabinets were unlocked with a drill months later.

Cabinet papers usually remain secret for 20 years after their production.

The ABC's revelation of its trove of documents, some classified "top secret", sparked an urgent investigation by the government department.

ASIO officer secured the documents in a safe on ABC premises earlier on Thursday after the papers were retrieved from Canberra, Melbourne and Brisbane.

The ABC said it had chosen not to publish many of the documents because of their classified nature.

© AAP 2018