– When the United States sought to punish Russia last month for its election interference and other aggressions, it targeted some of Russia’s wealthiest men, imposing sanctions on those viewed as enriching themselves off President Vladimir Putin’s government.

Now it turns out that one of the men, Viktor Vekselberg, was also singled out in another of the efforts to confront Russia’s election interference: the investigation led by the special counsel, Robert Mueller.

Federal agents working with Mueller stopped Vekselberg, a billionaire businessman, at a New York-area airport this year, searched his electronic devices and questioned him, according to people familiar with the matter. They confronted him after he stepped off a private plane about two months ago, according to one of the people.

There is no indication that Mueller suspects Vekselberg of wrongdoing. But Vekselberg attended the presidential inauguration last year, and the interest in him suggests the special counsel has intensified his focus on potential connections between Russian oligarchs and the Trump campaign and inaugural committee.

Though it is unclear what prompted Mueller’s investigators to approach Vekselberg, his widespread corporate interests and attendance at Trump’s inauguration are among the potential avenues for examination. Vekselberg also attended a December 2015 dinner in Russia where Michael Flynn, Trump’s first national security adviser, was also among the guests and sat beside Putin. The dinner was hosted by RT, the English-language television news network financed by the Kremlin.

Flynn was ousted weeks after the inauguration amid revelations he misled the vice president and others about his conversations with the Russian ambassador to the United States at the time. Flynn pleaded guilty in December to lying to the FBI and is cooperating with the special counsel.

Another potential area of interest for Mueller is Vekselberg’s business in Cyprus, the Mediterranean nation considered a magnet for Russian money. Vekselberg has controlled a company that has been the largest single shareholder in the Bank of Cyprus. Around the same time that Vekselberg was investing in the bank, Trump’s future commerce secretary, Wilbur Ross, was its vice chairman.

A spokesman for Mueller declined to comment; a lawyer and a spokesman for Vekselberg did not respond to requests for comment.

Vekselberg’s ticket to the inauguration came from his cousin and business associate Andrew Intrater. Intrater, an American who lives in New York, donated $250,000 to Trump’s inauguration, campaign finance records show.

Mueller’s investigators have questioned Intrater, according to a person briefed on the matter, though there is no indication that he is suspected of wrongdoing. A person close to Intrater said that he was encouraged to attend the inauguration by an American friend, and that he had wanted to use the trip as an opportunity to meet with business associates in Washington. Documents the person provided indicated that Intrater intended to hold business meetings during the weekend of the inauguration.

Intrater is the chief executive of Columbus Nova, an investment management firm whose biggest client is the Renova Group, Vekselberg’s sprawling conglomerate that operates in the energy sector and elsewhere.

At one point, Renova donated $50,000 to $100,000 to the Clinton Foundation.

The Trump administration’s decision to target Vekselberg and the Renova Group with sanctions underscored his perceived closeness to the Kremlin. The sanctions — against seven of Russia’s richest men and their companies as well as 17 top government officials — were aimed at penalizing those seen as enriching themselves from Putin’s government.

And yet, Vekselberg, a native of Ukraine, has long-running business ties to the United States. He founded Renova in 1990 as a Russian-American joint venture, according to an archived version of the company’s website.