The Australian Federal Police have executed search warrants on Labor Party offices in Melbourne as part of investigations into the leak of NBN documents.

News of the searches came to light about 7.30pm AEST on Thursday 19 May when Labor’s finance spokesman Tony Burke confirmed they were underway.

Though the AFP did not confirm the targets of the raids, they have been widely reported to be the offices of former Communications Minister Stephen Conroy and the home of two Labor staffers. The search of the home continued throughout the night.

AFP Commissioner Andrew Colvin said that documents seized in the searches had been sealed to await a determination over whether they are subject to parliamentary privilege.

AFP Comm: Parlt privilege has now been claimed on the documents seized overnight. The documents now sealed. (@lyndalcurtis)

— Sky News Australia (@SkyNewsAust) May 19, 2016

Tony Burke said the documents allegedly related to leaks concerning the NBN.

“There's no doubt the leaks that came from the NBN caused immense damage, immense damage to Malcolm Turnbull when they showed that the cost blowout of the NBN, the fact that it was slower, the fact that it was going to be delayed," Burke told the ABC’s 7.30 program.

The AFP said it had been referred allegations of “unauthorised disclosure of Commonwealth information” from NBN Co on December 9 last year.

It said that the investigation of the allegations was being “undertaken independent of government” and that the decision to raid the offices and homes was “made by the AFP alone”.

“Search warrants conducted in East Melbourne and Brunswick are part of a phased approach that the AFP has undertaken regarding this investigation,” the agency said.

“The next phase of this investigation involves the examination and analysis of material collected during these search warrants.”

The AFP said it had conducted a number of interviews with NBN employees in the lead-up to the searches.

A report by Fairfax Media said that up to 20 NBN staff had been interviewed, while Sky News later reported an NBN staffer had been “sworn in as a special constable to assist the AFP in its raids/investigation”.

An NBN staff member was sworn in as a special constable to assist the AFP in its raids/ investigation #nbn #auspol

— Kieran Gilbert (@Kieran_Gilbert) May 19, 2016

Shadow Attorney-General Mark Dreyfus told ABC’s Lateline program that the raids were “unprecedented and extraordinary events”, particularly given they occurred during an election campaign.

“I was shocked to learn that these events were occurring in the second week of an election campaign,” Dreyfus said.

“And I would repeat: these are extraordinary and unprecedented events and the Government has a great deal of explaining to do, a great many questions that the Government has to answer.

“The Government has to explain when it knew about this investigation, when it knew that the AFP were embarked on this and what the Government's view is of the appropriateness of this kind of police activity during an election campaign.”

However, the Minister for Industry, Innovation and Science Christopher Pyne said in a TV interview that the Government was also in the dark over the investigation and the search timings.

"If you're suggesting the government has organised raids by the AFP against the Labor party, that is an extraordinary allegation,” he told the Today Show.

The NBN has been hit by a series of damaging leaks over the past six months over the costs of the build, its timing, and technology choices.