Story highlights Richard Burr and Mark Warner are two senators who helm the Senate intelligence panel

Donald Trump Jr. and Jared Kushner met with a Russian lawyer in June 2016

(CNN) Sen. Mark Warner, the top Democrat on the Senate intelligence committee, told CNN the panel will ask Jared Kushner and Donald Trump Jr. for additional documents, following revelations from an email chain that Trump Jr released this week.

The Virginia Democrat would not say Thursday when the panel wants to interview Kushner or Trump Jr. But he added that the request for additional documents from Kushner was in part because he left off three meetings with Russians from forms submitted to the investigation.

"Again, I think it's not appropriate to go through the type of documents requested but we think it's very important that we have all of the appropriate information so we can ask the right questions," Warner said, adding later, "It seems strange to me that those meetings were at least conveniently forgotten, at least by Mr. Kushner."

Intelligence committee Chairman Richard Burr would not say Thursday when he wanted to speak with Kushner or Trump Jr.

"When we talk to somebody is when we already know what we want to learn from them," the North Carolina Republican told CNN. "I don't get into the timing. We've got a great metric of a lot of potential witnesses, and we knock out oh, two, three, as many as six every week."

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