The number of Facebook users whose personal information was accessed by Cambridge Analytica "could be higher" than the 87 million users acknowledged by Facebook, Wylie told NBC's Chuck Todd during a "Meet the Press" segment.

He added that his lawyer has been contacted by US authorities, including congressional investigators and the Department of Justice, and says he plans to cooperate with them.

"We're just setting out dates that I can go and sit down and meet with the authorities", he said.

The former Cambridge Analytica employee said that "a lot of people" had access to the data and referenced a "genuine risk" that the harvested data could be stored in Russia.

"It could be stored in various parts of the world, including Russia, given the fact that the professor who was managing the data harvesting process was going back and forth between the UK and to Russia", Wylie said.

Aleksander Kogan, a Russian data scientist who gave lectures at St. Petersburg State University, gathered Facebook data from millions of Americans. He then sold it to Cambridge Analytica, which worked with President Donald Trump's 2016 presidential campaign.

When asked if he thought Facebook could calculate the number of users affected, Wylie stressed that data could be copied once it leaves a database.

"I know that Facebook is now starting to take steps to rectify that and start to find out who had access to it and where it could have gone, but ultimately it's not watertight to say that, you know, we can ensure that all the data is gone forever", he said.