Washington (CNN) Senate intelligence committee investigators have spoken with several Russians who attended a June 2016 Trump Tower meeting with Donald Trump Jr., a sign that the matter remains a significant focus for lawmakers looking into potential coordination between Trump associates and Kremlin-linked operatives during the presidential campaign.

Sen. Richard Burr, the chairman of the Senate intelligence committee, told CNN that the panel has interviewed some of the Russians who were at that meeting, which Trump Jr. attended after being promised dirt on the Clinton campaign and being informed that the Russian government wanted his father to win the presidency. Paul Manafort, who was then the Trump campaign chairman, along with the President's son-in-law, Jared Kushner, also attended the meeting.

The intelligence committee has previously met with both Kushner and Manafort, but has not yet brought in Trump Jr. Burr said the committee is "sequencing" its interviews to speak with everyone else "involved in the meeting before we know exactly what we want from Don Jr."

Burr, R-North Carolina, would not say which Russians, or how many, investigators have spoken with. Committee officials declined to comment further.

At the same time, a second Senate panel, the judiciary committee, which met privately with Trump Jr. last month, is trying to finalize plans to bring the President's son in for a public hearing -- something one committee source said could happen as soon as this month.

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