George Nader, a Lebanese American businessman who helped organize and attended the Seychelles meeting, has testified on the matter before a grand jury gathering evidence about discussions between the Trump transition team and emissaries of the Kremlin, as part of Mueller’s investigation into Russian efforts to interfere with the 2016 election.

Nader began cooperating with Mueller after he arrived at Dulles International Airport in mid-January and was stopped, served with a subpoena and questioned by the FBI, these people said. He has met numerous times with investigators.

Last year, Prince told lawmakers — and the news media — that his Seychelles meeting with Kirill Dmitriev, the head of a Russian government-controlled wealth fund, was an unplanned, unimportant encounter that came about by chance because he happened to be at a luxury hotel in the Indian Ocean island nation with officials from the United Arab Emirates.