New book 'The Burglary' reveals who committed famous break-in at the FBI

On March 8, 1971, burglars broke into an FBI office outside Philadelphia and stole thousands of files, exposing a covert campaign to spy on anti-war activists and other dissidents the law enforcement agency suspected of subversive behaviour.

After the embarrassing break-in, FBI director J. Edgar Hoover ordered hundreds of agents to try to catch the perpetrators. Despite all its resources, the agency couldn't find them.

While the case floundered, the incriminating documents surfaced in newspapers nationwide, disclosing a dark period in the FBI's history and humbling the powerful Hoover.

The stolen material was the first glimpse of an agency operation called Cointelpro — an illegal and secret surveillance programme targeting Americans, and one that used dirty tricks and smear tactics.

On Tuesday, some of the burglars involved in the break-in were finally identified, in a book by former reporter with The Washington Post, Betty Medsger, who first wrote about the stolen documents in 1971.

Because a statute of limitations has long passed, those responsible cannot be prosecuted.