WASHINGTON - President Donald Trump’s eldest son was questioned behind closed doors Thursday by Senate investigators over possible connections between his father’s 2016 campaign and Russia. Donald Trump Jr, who serves as executive director of the Trump Organization, avoided news cameras and reporters and entered a meeting in the US Capitol complex with investigators of the Senate Judiciary Committee.

He gave an opening statement lasting 10 to 15 minutes, Senate Democrat Dick Durbin told reporters. Trump Jr, 39, became a key figure in the Russia probe after he agreed to a meeting with a lawyer linked to the Kremlin in June 2016.

Investigators probed Trump Jr over his participation in the meeting. “That’s what this is about,” Durbin said. “That is the crucial event.” The meeting at Trump Tower in New York, in which the campaign team was promised dirt on Donald Trump’s rival Hillary Clinton, was also attended by Trump’s son-in-law Jared Kushner and then-campaign manager Paul Manafort.

The panel’s interview of Trump Jr was similar in format to that of Kushner, who met with Senate and House intelligence committee staffers to discuss his ties to Russia.

Kushner emerged from those meetings to stress that he “did not collude with Russia,” and that his undisclosed meetings with Russian officials were “proper.”

Trump Jr acknowledged in July that he met last year with the lawyer, who was presented as an emissary of the Russian government in possession of potentially compromising information on Clinton.

But Trump Jr argued that the meeting amounted to nothing and that no collusion took place.

President Trump has also consistently rejected any idea of collusion, as has the Kremlin.

Congressional committees investigating Russia’s alleged efforts to sway last year’s US presidential election in Trump’s favor have sought to learn whether members of the Trump team conspired with Russia.

The committees have demanded documentation from and interviews with various campaign protagonists, including those in Trump’s inner circle. Lawmakers have indicated that some of them could be called to testify in public hearings.

Investigations by congressional committees are distinct from those conducted by Robert Mueller, the special prosecutor appointed by the Department of Justice.