Virginia Sen. Mark Warner told CNN that Mueller has "tools we don't have" to investigate financial issues. He did not rule out that his committee was also investigating possible money laundering or other financial issues that could be tied to the Russia probe, but said that it "clearly falls into the scope" of the Mueller investigation.
"At least to me that falls more into what would be criminal activity but those are discussions that will be ongoing," Warner said.
In an op-ed published Tuesday
, Fusion GPS co-founders Glenn Simpson and Peter Fritsch said they urged congressional investigators to "look into the bank records of Deutsche Bank and others that were funding Mr. Trump's businesses."
"We found widespread evidence that Mr. Trump and his organization had worked with a wide array of dubious Russians in arrangements that often raised questions about money laundering. Likewise, those deals don't seem to interest Congress," they wrote.
In addition, the issue of money laundering and Russia was thrown back into the spotlight Wednesday on the heels of excerpts from a new book from Michael Wolff published by The Guardian
where President Donald Trump's former chief strategist Steve Bannon said the Russia investigation was "all about money laundering."
"Their path to f***ing Trump goes right through Paul Manafort, Don (Trump) Jr., and Jared Kushner ... It's as plain as a hair on your face," Bannon reportedly said.
The White House responded Wednesday that Bannon "lost his mind,"
and Trump Jr.'s attorney declined to comment.
Deutsche Bank has loaned billions of dollars to Trump since the 1990s, and Trump still owes roughly $300 million to the bank, according to an estimate from Bloomberg. Trump's critics have called on the bank to release information about Trump's accounts and affirm that none of the cash is linked to Russia, though Deutsche has balked at those requests.
Deutsche Bank declined to comment on whether it has been subpoenaed by the special counsel. The bank has previously refused to comply with requests for information about Trump finances from House Democrats, who lack subpoena power. The bank has declined to release information to Congress, citing privacy among other concerns.
The special counsel has charged former Trump campaign chairman Paul Manafort and his deputy Rick Gates for financial crimes unrelated to the 2016 election. They have both pleaded not guilty.
The House and Senate intelligence panels have received some financial data from the Treasury Department's financial crimes unit, known as FinCEN, which investigates money laundering and has previously examined violations by Trump's casinos.
A Democratic procedural effort to force the House Financial Services Committee to subpoena the bank was rejected by the committee's chairman, Republican Rep. Jeb Hensarling of Texas, last year. Sen. Ron Wyden of Oregon has also sought to use his perch as the top Democrat on the Senate Finance Committee to obtain more Treasury financial documents under his committee's purview.
"There's been a number of members who raised issues about the Trump Organization finances for some time," Warner said. "Sen. Wyden, for example, and I think it is appropriate, whether it's in the purview of our investigation or special prosecutor Mueller, that's an open question, but it appears at least that the special prosecutor is definitely following that track."
Senate Intelligence Chairman Richard Burr, a North Carolina Republican, has previously said that his committee is not investigating criminal matters tied to Russian election meddling, as that's the special counsel's lane. Burr has also declined to comment on subpoenas.
Warner declined to comment Wednesday on subpoenas involving Deutsche Bank.
Simpson has testified before three congressional committees investigating Russian election meddling, though the Fusion GPS op-ed appeared directed at the House committee, where Democrats have complained that the Republican-led probe hasn't dived into financial matters.
The op-ed sparked a fight between congressional Republicans and Fusion GPS Wednesday over the firm's demand for the committees to release interview transcripts.
Burr and Senate Judiciary Chairman Chuck Grassley of Iowa both said that an invitation for Simpson to testify publicly remained on the table.
"Given that Fusion seems to have more to say, if Mr. Simpson and Mr. Fritsch would like to return to the Committee for an open hearing, we will certainly entertain such an event," Burr tweeted
Grassley spokesman Taylor Foy argued there were "investigative factors ... like tainting the memory of other witnesses," which was why the committee did not intend to release the transcript.
Over in the House, the top Democrat on the intelligence panel, Rep. Adam Schiff of California, said he supported releasing the Simpson transcripts, noting the committee has previously released interview transcripts of onetime Trump foreign policy adviser Carter Page and Blackwater founder Erik Prince.
Fusion GPS attorney Joshua Levy responded that Simpson should be treated "equitably" with others in the Trump team who were also threatened with subpoenas.
"Having had the opportunity to review the full transcript, Fusion GPS wants it released," Levy said.