(CNN) House Intelligence Chairman Adam Schiff said on Tuesday night that his committee is still looking into the identity of the person who Rudy Giuliani was speaking with and had the obscured phone number of "-1" -- and whether that person is President Donald Trump.

"We can't confirm yet who" the number belongs to, Schiff said during an interview on CNN's "Anderson Cooper 360."

"We are certainly investigating that," Schiff said. "Rudy Giuliani only had one client -- and that was Donald Trump."

Schiff noted in the interview that the phone number -1 also came up during the trial of former Trump adviser Roger Stone.

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