Secretary of Commerce Wilbur Ross' financial dealings have once again caught the media's attention.

This week, PBS Newshour hosted Forbes associate editor Dan Alexander for a talk on Ross' shareholding in Greenbrier Railcar Co and Bermuda-based bulker owner Nautical Bulk Holdings.

PBS Newshour journalist Amna Nawaz questioned Alexander on Ross' dealings with these companies while serving as commerce secretary since late February 2017.

Nawaz opened the seven-minute segment with a letter from the federal Office of Government Ethics criticising Ross for failing to fully divest stocks by 15 January 2017 -- 18 months after he said he would do so.

She said Ross admitted to committing "inadvertent errors" and said he has since divested all of his stocks but questions remain with regards to his finances while in office.

In late June, Citizens for Responsibility and Ethics in Washington filed criminal and ethics complaints against the former Navigator chairman with the Department of Justice and the Office of Government Ethics.

Lunch with Greenbrier CEO

In his reporting for Forbes, Alexander has focused on an 18 May 2018 lunch that Ross had with Greenbrier chief executive Bill Furman and Ross' secretary of staff Wendy Teramoto.

"At the time, Wilbur Ross had a secret interest in Greenbrier, which he had never disclosed to ethics officials," he said.

"In addition, Wendy Teramoto also had a financial interest in Greenbrier, so you have three people at the meeting, two people who have undisclosed interests in the company that the third person is running."

Greenbrier also owns Jones Act shipbuilder Gunderson Marine.

Alexander said Geenbrier had been lobbying for renegotiations of the North American Free Trade Agreement, and Ross announced later that day that he would be doing just that.

Ross' stake in Nautical Bulk Holdings

Alexander also said Ross had a stake in Nautical Bulk Holdings, a Bermuda-based drybulk owner that in 2013 raised $100m in equity capital for eight newbuilds at China's Jiangsu Hantong Ship Heavy Industry shipyard.

"At the time, Wilbur Ross is one of Trump's lead lieutenants in the ongoing trade war between the United States and China," he said.

"You've got a guy whose financial interests are positioned to benefit from trade in China at the same time he is negotiating over trade in China."

Alexander also pointed out that Ross has said he forgot about his $10m investment in his former employer Invesco.

"It's very difficult to believe that a guy who is known as one of the smartest investors in the US could have simply forgotten about, for example, a $10m stake that he still held with his former employer," he said.

'No conflict of interest'

The Commerce Department said the lunch with Furman, Ross and Teramoto was "purely social" and paid for by Ross himself.

"No items specific to Greenbrier have been before the Secretary during his tenure at Commerce," the agency said.

"Secretary Ross informed ethics officials of his Greenbrier holdings before taking office, but this holding was inadvertently omitted from his final disclosure. As previously mentioned, he divested of his holdings of Greenbrier last fall."

The department said there was 'no conflict of interest' regarding Ross' and Teramoto's stake in Nautical Bulk Holdings.

"Secretary Ross and Wendy Teramoto have not taken any action with a direct and predictable effect on their financial holdings," he said.

"Secretary Ross divested his interest in Greenbrier last fall and has committed to sell his stake in Nautical Bulk Holdings."