(CNN) The Treasury Department is cooperating with a Senate Republican investigation into Hunter Biden's activities in Ukraine, according to a top Democrat on one of the committees.

Sen. Ron Wyden of Oregon, the ranking Democrat on the Senate Finance Committee, criticized the Treasury Department for sending over information after it had stonewalled the House's impeachment inquiry into President Donald Trump's dealings with Ukraine.

Wyden's office is not saying what documents were turned over and whether they specifically involve Hunter Biden, the son of former Vice President Joe Biden. Three Republican chairmen -- Finance Chairman Chuck Grassley of Iowa, Homeland Security Chairman Ron Johnson of Wisconsin and Judiciary Chairman Lindsey Graham of South Carolina -- have sent letters in recent months seeking information and interviews related to the Bidens, the Ukrainian natural gas company Burisma and uncorroborated allegations about Ukrainian interference in the 2016 US election. Trump and his allies have repeatedly made unfounded and false claims to allege that the Bidens acted corruptly in Ukraine.

"For its part, the Trump administration refused to comply with all Democratic requests for documents and witnesses associated with impeachment. Applying a blatant double standard, Trump administration agencies like the Treasury Department are rapidly complying with Senate Republican requests -- no subpoenas necessary -- and producing 'evidence' of questionable origin," Wyden spokeswoman Ashley Schapitl said in a statement. "The administration told House Democrats to go pound sand when their oversight authority was mandatory while voluntarily cooperating with the Senate Republicans' sideshow at lightning speed."

A Treasury spokesman did not respond to a request for comment.

Grassley spokesman Taylor Foy said, "As a matter of routine, we don't discuss sensitive third-party material during ongoing investigations. It's unfortunate that Democrats whom we've kept in the loop on our investigations would recklessly seek to interfere with legitimate government oversight."

The Senate Republican investigation into the Bidens, which is being led primarily by Grassley and Johnson, is a sign that while impeachment has ended, the investigations related to Ukraine have not. House Democrats too are still pursuing probes and court cases post-impeachment, and many Democrats want the House to subpoena former national security adviser John Bolton, who was not called in the Senate trial, after senators voted not to hear from witnesses.

It is not clear what Treasury has provided to the Senate committees, which was first reported by Yahoo News . Grassley and Johnson sent a letter dated November 15, 2019 to the director of the Financial Crimes Enforcement Network, Ken Blanco, requesting information related to their investigation "into potentially improper actions by the Obama administration with respect to Burisma Holdings and Ukraine." Johnson and Grassley requested "all Suspicious Activity Reports" -- which financial institutions are required to file when they spot suspicious activity, though the reports don't necessarily indicate wrongdoing occurred -- that were filed related to 11 individuals or entities including Hunter Biden and Burisma Holdings by December 5, 2019.

In addition to the Treasury letter, the Senate Republicans chairmen requested information late last year related to Ukraine from Secretary of State Mike Pompeo and Attorney General William Barr. In a sign they are still expanding their probe, they sent a new letter on Wednesday to the Secret Service seeking travel information on Hunter Biden.

During the impeachment trial, Trump's lawyers and congressional Republicans defended the President's actions by saying he had legitimate reasons to worry about corruption Joe Biden and Hunter Biden, the latter of whom who worked for Burisma. Multiple witnesses in the impeachment inquiry testified that Biden's actions in Ukraine were consistent with official US government policy, backed by European allies and both Republicans and Democrats in Congress, including Johnson.

In the House, Democrats are still weighing their next steps following the end of the Senate impeachment trial. They never received documents from the Trump administration related to Ukraine, some of which have been released in the weeks since the President was impeached in December thanks to Freedom of Information Act lawsuits. There's also the question of Bolton, who indicated he was willing to testify in the Senate but has not said the same about the House.

House Judiciary Chairman Jerry Nadler, a New York Democrat, said Wednesday that it was likely the House would subpoena Bolton, but House Intelligence Chairman Adam Schiff has not committed to doing so. "We really haven't made any decisions yet," the California Democrat said Thursday when asked about the House's next steps.

In addition to Ukraine threads, House Democrats still have active court cases in their efforts to obtain the President's tax returns , financial and accounting information and the testimony of former White House counsel Don McGahn . Democrats said they expect those investigations into the President to continue, regardless of having already impeached him -- and the committees will continue aggressive oversight of the federal agencies.

"No one thinks that the Senate's act of jury nullification gives the President any immunity from the Congress' oversight power," said Rep. Jamie Raskin, a Maryland Democrat on the Oversight and Judiciary committees. "So we will not let up for one second in ferreting out the corruption and the criminality that have overtaken the administration. I believe our oversight power is as necessary as ever, if not more so now. This President appears to be emboldened by the robotic behavior of Republican senators with the notable exception of Mitt Romney."

House Speaker Nancy Pelosi on Thursday noted the ongoing court cases but didn't suggest the Democrats were about to make a new push for testimony from Bolton or others.

"Those cases still exist," the California Democrat said at her weekly news conference. "If there are others that we see as an opportunity, we'll make a judgment at that time. But we have no plans right now."