The concerns center on the extent of foreign investment in a series of finance entities Mnuchin helped manage, including one based offshore in the Cayman Islands, aides tell CNN.

It's an issue -- which Democratic aides and lawmakers say hasn't been addressed in subsequent follow-up questions in the weeks since -- that has raised concern about the extent of the influence those investors may hold, and the potential for conflicts of interest not unlike what has tailed Trump throughout his campaign. On its face, it echoes a prime point of contention for Democrats probing all of Trump's Cabinet picks, many of whom boast extensive private business and finance ties.

But Mnuchin is slated to be the Trump Administration's top economic official, making those ties even more susceptible to potential conflicts, aides say -- the types of potential conflicts Mnuchin himself appeared to draw attention to inadvertently during his confirmation hearing.

The focus has trained on a series of finance entities, all offshoots of the hedge fund run by Mnuchin up until he was selected as Trump's pick to be the country's economic point person.

Foreign investors

Asked specifically about the investment makeup of the offshore entity during his hearing, Mnuchin repeatedly said it was created to provide opportunities for pension funds and non-profits to invest. There were also "a small number of foreign investors," Mnuchin told lawmakers.

But the offshore entity and a series of other finance vehicles, some of which weren't originally disclosed by Mnuchin during the financial disclosure process, hold gross assets of more than $240 million, according to an SEC filing reviewed by CNN. Significant percentages of each were held by foreign investors, according to the filing, and one was 100 percent owned by foreign investors.

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Mnuchin's failure to initially disclose his relationship with the funds, along with his minimizing the scope of foreign investment in them during the hearing, has Democrats questioning whether it was part of a deliberate effort to steer them away.

"Misleading -- and that's the most charitable way you could say it," Sen. Ron Wyden, the top Democrat on the Senate Finance Committee, said of Mnuchin's explanation during an interview. "You walked away thinking that almost the only people were churches and pensions (investing in those entities.)"

One fund, Dune Capital International LTD., listed a gross asset value of $35.1 million in the 2013 disclosure. The disclosure, which identifies Mnuchin as one of three "Partners and Directors" of the Cayman Islands-based entity, claims 28% of the underlying fund ownership came from foreign investors, according to the SEC filing reviewed by CNN.

A second US-based entity with $18.4 million in gross asset value, DE International Holdings LLC, is listed as 100% owned by "non-US persons," according to the SEC filing.

Dune Entertainment Holdings LLC, which had a gross asset value of $124.8 million, listed 43% of its ownership as coming from foreign persons or entities. Two additional entities, Dune Entertainment International and Dune Entertainment LP, held in total nearly $62 million in gross asset value. The underlying assets were 100% and 43% beneficially owned by non-US persons, respectively. The portfolio played a role, at least in part, in the financing of Mnuchin's extensive financing of Hollywood projects.

"We're talking about foreign investors," Wyden said. "I don't have a lot of evidence right now that all these non-profits and pensions were interested in investing in movies."

The foreign investment in the offshoots was entirely legal and isn't required to be disclosed. But Mnuchin's role in the entities was supposed to be disclosed to the committee. It wasn't. At least not until the Democratic investigative staff on the panel discovered the SEC document.

Missing paperwork

Mnuchin, for his part, blamed the missing paperwork on the byzantine nature of the disclosure process. In a private interview with committee staff, aides said, Mnuchin acknowledged that his responses to the committee had not, as he had stated, been "true, accurate and complete." He twice was forced to revise his initial disclosure questionnaire. He stated his role in the entities was "inadvertently missed" during the disclosure process.

Mnuchin's confirmation spokesman didn't respond to multiple requests for comment for this story. A White House official said the SEC filing, along with the rest of Mnuchin's extensive financial documentation, is now available for anyone to see.

"Mr. Mnuchin has followed all the necessary rules and regulations for his confirmation process," the official said in a statement. "All of this information is now publicly available and can be found by anyone who wishes to look at Mr. Mnuchin's financial records."

Mnuchin, as it currently stands, is on track to be confirmed.