The FBI and CIA are investigating hundreds of possible suspects in one of the biggest security breaches in CIA history, CBS News reports. The WikiLeaks “Vault 7” release, which contained thousands of top-secret documents, revealed the agency’s hacking tools.

A joint investigation and manhunt by the Federal Bureau of Investigation and the Central Intelligence Agency into the source of WikiLeaks’ “Vault 7” dump last month has begun, CBS News justice and homeland security correspondent Jeff Pegues reported Wednesday evening.

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The release last month brought to light the CIA’s digital arsenal for hacking into computer systems and smart devices such as phones and televisions. Thousands of top-secret classified files that had previously been guarded within a “highly secure section of the intelligence agency,” as CBS News sources described it, were made available to the world for free by WikiLeaks.

The source of the leak, the FBI and CIA reportedly believe, was one of the hundreds of agents or contractors who had physical access to the material, not an outside hacker. That suspicion seems to align with what WikiLeaks said in their press release announcing the Vault 7 release on March 7.

“The archive appears to have been circulated among former US government hackers and contractors in an unauthorized manner, one of whom has provided WikiLeaks with portions of the archive,” the pro-transparency group said.

Unnamed US intelligence sources told Reuters within a day of the release that the CIA had been anticipating it since near the end of 2016.

The FBI and CIA coordinated reviews of the incident and a criminal investigation was opened within a day of the release, the Washington Post reported at the time, based on an unnamed former intelligence official who said to expect "another major mole hunt."

Former CIA Deputy Director Mike Morell told CBS News less than a week after the release that the leak “has to be an inside job,” as the data was on a CIA top secret network “not connected to any other network.”

What makes this look real?

Program & office names, such as the JQJ (IOC) crypt series, are real. Only a cleared insider could know them. — Edward Snowden (@Snowden) March 7, 2017

Former NSA contractor and whistleblower Ed Snowden tweeted hours after the release that "only a cleared insider" could be responsible for the leak.

Last week, in his first public comments in his new position, CIA director Mike Pompeo blasted WikiLeaks as “a non-state hostile intelligence service often abetted by state actors like Russia” and called founder Julian Assange a “demon.”

Assange on Wednesday hit back at Pompeo on ‘The Intercepted’ podcast with Jeremy Scahill of The Intercept, accusing him of attacking WikiLeaks "to get ahead of the publicity curve.”

"In fact, the reason Pompeo is launching this attack is because he understands we are exposing in this series all sorts of illegal actions by the CIA, so he’s trying to get ahead of the publicity curve and create a preemptive defense," Assange said.

READ MORE: ‘All sorts of illegal actions by CIA’: Assange blasts Pompeo for ‘pre-emptive attack’ on WikiLeaks