Mark Zuckerberg tried to assure American lawmakers worried that Russia and or other foreign powers will use the social media network to meddle in upcoming midterm elections.

(Leah Millis/Reuters)

Testifying for the first time publicly the 33-year-old Facebook CEO said ”it was clearly a mistake” to believe data-mining company Cambridge Analytica deleted Facebook data it had gathered from 87-million users in an attempt to sway election.

Zuckerberg apologized, as he has in the past, and said he’s ”responsible” for what happens on Facebook.

He’s also reiterated that the company’s in the process of investigating apps, ”many apps,” in the tens of thousands, that had access to user information.

Zuckerberg testified before a joint session of two Senate committees today and will go before a House of Representatives panel Wednesday.