US intelligence and law enforcement officials, speaking on condition of anonymity, told Reuters on Wednesday that the CIA had been aware of the impending leak of its cyberwarfare arsenal since the end of last year.

The unnamed officials also confirmed that an internal investigation by the agency into the source of the leak is focused primarily on contractors, who the agency believe passed the documents to WikiLeaks.

They also stated their belief that the 8,761 documents contained within the current “Year Zero” leak, the first of the “Vault 7” series, appear to be authentic. On Wednesday, the FBI also announced its federal criminal investigation into WikiLeaks following the latest release and stated that it will be coordinating their efforts with the CIA.

READ MORE: FBI investigating Wikileaks’ vault 7 disclosures on CIA hacking

The leak has already been described by experts as potentially more significant than the NSA leaks by Edward Snowden in 2013, the Wall Street Journal reported.

WikiLeaks’ publication of a massive batch of covert documents detailing the hacking techniques used by the CIA poses a multitude of uncomfortable questions for world leaders, law enforcement and even WikiLeaks itself.

In one poll tweeted earlier Wednesday, the transparency group asked whether it should work more closely with the tech industry to help shore up cyber defenses around the world.

Tech companies are saying they need more details of CIA attack techniques to fix them faster. Should WikiLeaks work directly with them? — WikiLeaks (@wikileaks) March 8, 2017

WikiLeaks says that the classified information contained in the leaked documents was “lost” by the CIA and subsequently “circulated among former US government hackers and contractors in an unauthorized manner.”

One of those individuals is then said to have provided the whistleblowing website with the relevant content.

According to WikiLeaks a secure upload submission option, in which no identifying data about a source is recorded, is offered. WikiLeaks has not said if the identity of the source is known to the organization.

READ MORE: Apple, Samsung, Microsoft: WikiLeaks blows lid on scale of CIA’s hacking arsenal

WikiLeaks stated on Twitter that the information revealed so far in Year Zero accounted for “less than 1 percent” of the total series of publications. More releases are expected but when they will occur is unknown.

WikiLeaks has released less than 1% of its #Vault7 series in its part one publication yesterday 'Year Zero'. — WikiLeaks (@wikileaks) March 8, 2017

It has also not announced the number of documents and files it plans to release or the frequency of release – unlike last year’s Podesta email leak where it released emails from the Democratic National Committee (DNC) each day in the run-up to the US election.

READ MORE: WikiLeaks says just 1% of #Vault7 covert documents released so far

WikiLeaks claims the cache of documents and files released originated from within the CIA’s Center for Cyber Intelligence in Langley, Virginia. The CIA have not confirmed if the documents are authentic.

“We do not comment on the authenticity or content of purported intelligence documents,” Jonathan Liu, a spokesman for the CIA, told The Washington Post.

Ex-CIA Director Michael Hayden appeared concerned by the release, telling the BBC: "If what I have read is true, then this seems to be an incredibly damaging leak in terms of the tactics, techniques, procedures and tools that were used by the Central Intelligence Agency to conduct legitimate foreign intelligence.”

"In other words, it's made my country and my country's friends less safe."

Edward Snowden tweeted that the leak, which consists mainly of HTML files and PDF documents, “looks authentic,” adding to the feeling that the files are genuine.

READ MORE: WikiLeaks CIA Vault 7: 'We are looking at George Orwell’s 1984’

Year Zero has highlighted the extent of the CIA and MI6’s spying capabilities. The two intelligence agencies were revealed to have held a joint workshop on hacking into Samsung smart TVs, allowing them to listen to audio via the devices, even when powered off.

The leak also revealed that vulnerabilities in Google’s Android Operating System, used in 85 percent of the world’s smart phones, allowed it to be “weaponized” by the CIA using hacking code.

The techniques allow the CIA to access data from social messaging platforms, including WhatsApp, Weibo and Clockman before encryption, according to WikiLeaks.