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CANBERRA, Australia — The Australian government on Wednesday launched an urgent investigation into the loss of thousands of classified documents that were sold with two second-hand filing cabinets and later obtained by a major news outlet.

The cabinets were sold by a Canberra furniture shop at a discount price because they were locked and no one could find keys, the Australian Broadcasting Corp. reported.

The ABC has not identified the buyer who they said purchased the cabinets for small change and left them unopened for months, before removing the locks with a drill only to find thousands of Cabinet documents spanning more than a decade and four prime ministers, the most recent being Tony Abbott. Abbott was replaced in 2015 by the current Prime Minister Malcolm Turnbull.

Australian Prime Minister Malcolm Turnbull Dean Lewins / EPA file

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The ABC has not said when the documents were found. But it has used them in recent weeks to report stories that have been embarrassing to the former administrations of Prime Minister Kevin Rudd and Abbott as well as a number of serving lawmakers.

The ABC reported nearly all the documents are classified. The classifications include "top secret," "sensitive," and ''Australian eyes only."

The state-owned broadcaster said it had chosen not to report some documents on national security grounds.

The documents cover Australia's intelligence priorities and counterterrorism planning. They detail missile upgrades, profiles of suspected militants and Australia's desire in 2010 for more Indonesian cooperation to stop asylum-seekers reaching Australian shores in fishing boats, the ABC said.

One document refers to an audit that revealed that the Australian Federal Police had lost almost 400 national security files over five years ending 2013.

The documents also reveal that a former finance minister left 195 top-secret papers in her old office when her government was voted out in 2013.

Australian Cabinet documents are usually kept secret for 20 years, before they are made public in a heavily redacted form.

Rory Medcalf, head of the Australian National University's National Security College, described the discarded documents as "very weird and embarrassing" from a national security and political perspective.

Australia's allies, including the United States, "would be concerned," Metcalf said.