The CIA and FBI have launched a joint investigation into who was behind the breach of thousands of top-secret documents that ended up on the WikiLeaks website.

The leaker is believed to be one of hundreds of CIA employees who would have had access to information about how the federal agency hacks smartphones, smart televisions and computers. It also could have been a federal contractor.

WikiLeaks published the information in March. The breach was one of the worst security incidents in the agency's history.

CIA Director Mike Pompeo recently blasted WikiLeaks founder Julian Assange for the first time since assuming his role in the Trump administration despite the president's support for the organization during the campaign.

"It is time to call out WikiLeaks for what it really is: A non-state hostile intelligence service often abetted by state actors like Russia," Pompeo said.

The CIA has not confirmed whether the information was authentic.