(CNN) Investigators on the House intelligence committees have obtained access to valuable data from the Treasury Department, a development that will open their doors to investigate possible connections between President Donald Trump's business empire and Russians, CNN has learned.

Investigators received access to the financial data this week, according to multiple sources with knowledge of the development.

Sen. Mark Warner, the top Democrat on the Senate intelligence committee told reporters Thursday that his committee also had gotten the Treasury Department data.

The Treasury Department's Financial Crimes Enforcement Network -- or FinCEN -- monitors global financing and frequently investigates money laundering. The agency collects data from banks around the world and is a critical source in identifying how shell companies move money.

"While I cannot confirm any briefings or requests made by the House Intelligence Committee, I will say that examining financial records and transactions is absolutely crucial to our investigatory effort," Rep. Adam Schiff, the top Democrat on the House Russia investigation, told CNN Thursday.

Democratic lawmakers have been saying for months now that they need to follow the money, and have amplified those calls in recent weeks.

Warner grilled Treasury Secretary Stephen Mnuchin Thursday on Treasury's continued cooperation with the Senate probe. Earlier in the week, Warner questioned Trump's nominee to oversee FinCEN at the Treasury Department, Sigal Mandelker. Warner, in his testimony, referenced a May 4 meeting at his office with Mandelker.

"We requested documentation from FinCEN that will be absolutely critical to the Russia investigation. Our ask included things like the FinCEN flash notices. I know that we've received a preliminary response from treasury that they're quote unquote 'working on it,'" Warner told Mandelker this past Tuesday. "Well, I've got to tell you, that's not good enough in an investigation that is so critical it is dominating the news."

Sen. Ron Wyden, an Oregon Democrat on the Russia investigation, placed a hold on Mandelker's nomination until FinCEN provided documents requested by Senate investigators on April 26. It was not immediately clear Thursday if Wyden had lifted his hold.