Republican Sens. Chuck Grassley (Iowa) and Ron Johnson (Wis.) announced a review on Wednesday of "potential conflicts of interest posed by the business activities of Hunter Biden and his associates during the Obama administration."

Why it matters: The announcement came roughly one hour after the Senate voted to acquit President Trump on both articles of impeachment. Trump's request for Ukraine to investigate Hunter and Joe Biden over unsubstantiated corruption claims is ultimately what sparked his impeachment.

Details: The review was announced in a letter to Secret Service Director James Murray. It states the Finance Committee and Homeland Security and Governmental Affairs Committee will look into Hunter Biden's business activities in Ukraine and China.

"We write to request information about whether Hunter Biden used government-sponsored travel to help conduct private business, to include his work for Rosemont Seneca and related entities in China and Ukraine," Grassley and Johnson write.

The senators also ask for information on "the protective detail that Hunter Biden received while his father was Vice President," and a "list of all dates and locations of travel, international and domestic, for Hunter Biden."

A spokesperson for Democratic Sen. Ron Wyden said Thursday that the Treasury Department has complied with a request from Republican senators seeking documents on Hunter Biden’s business relationship with Burisma, the Ukrainian gas company at the center of President Trump's impeachment, the New York Times reports.

"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.

“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.”

Read the letter.

Go deeper: Hunter Biden defends his Ukraine work